Q. Our 2-month-old boy is very colicky. Nothing I do seems to stop his crying. Should I try some cereal, change his formula, or what?

A. Colic is unexplained crying spells generally occurring between three weeks and three months of age. Let me emphasize that no one really knows what causes it, although many parents think it has something to do with intestinal gas, diet or substances transmitted in breast milk. Some parents try all sorts of dietary changes, often to no avail. And just as they're at their wits' end, the colic miraculously seems to clear up.

Colic may be part of some babies' normal development or a sign of a strained parent-infant relationship. One theory is that late-night feedings and little sleep makes for weary parents, and this coupled with anxiety or frustration at a demanding baby leads to tension that the baby senses and responds to by crying fits. It's interesting that colic seems to stop just about the time most babies (and parents) are sleeping through the night.

Another theory is that the baby's intestines are not fully developed and don't absorb milk sugar (lactose) very well, which provokes cramps. Finally, colic may represent an infant's expression of an unmet need.

If your baby is crying for no apparent reason, consider these possibilities in whatever order you think best at the time. Your baby: is hungry and wants to be fed; wants to suck although he's not hungry; wants to be held; is bored and wants stimulation; is tired and wants to sleep.

If these measures fail, and your doctor says the baby is healthy, it may be best to let your baby cry, and get some rest and relaxation for yourself.

Q. I'm 43 years old and have started experiencing extreme breast fullness and tenderness before my menstrual period. Do I have premenstrual syndrome (PMS)? Could this be a sign of menopause? What can I do about it?

A. You have premenstrual symptoms, but not premenstrual syndrome in the usual sense of the term. Although there is no universally accepted definition of PMS, it is generally thought to include any grouping of the following symptoms: premenstrual nervousness, irritability, crying spells, mood swings, depression, poor concentration, abdominal bloating, fluid retention, weight gain, headache, fatigue and breast swelling.

Because you only have breast fullness, I don't think you fit the typical syndrome.

Premenstrual swelling of the breasts is related to fluctuations in female hormones, like estrogen and progesterone. Because the production of these hormones becomes somewhat irregular as menopause approaches, your symptoms may be part of early menopausal changes, especially since you didn't used to get breast fullness before your periods.

Treatment may help relieve your symptoms, but probably won't make them go away entirely. I'd suggest starting with simple pain relievers, like aspirin or acetaminophen (Tylenol and other brands).

If your symptoms are very troublesome, you may want to ask your doctor about taking female hormones such as those found in birth control pills, or plain progesterone-like hormones.

Many other remedies have been tried, but not proven, including vitamin B6 and avoidance of caffeine, especially for women with so-called fibrocystic breasts. Also, you might benefit from taking diuretics (fluid pills) each month before you expect symptoms to develop. Q. I get herpes fever blisters on my lips. I know that a newborn can get serious herpes infection if born through an infected birth canal. Is it also possible for herpes on the face to get into the bloodstream and affect a developing fetus? A. Herpes infection of the face or other skin areas can't pass through the body to affect the fetus.

The main problem with herpes infections in pregnancy is the one you mention -- contamination of a newborn passing through a birth canal infected with herpes. This problem is usually overcome by careful checking of the mother during the last weeks of pregnancy to make sure she doesn't have active genital herpes infection. If she does, the infant is delivered by cesarean birth.

Once the baby is born, there is some risk of transmitting herpes infection if a parent has fever blisters or other active herpes skin infection. The mother or father may see and touch the infant provided that the skin infection is covered and the hands are carefully washed. For example, wear a mask for fever blisters on the lips and gloves for a hand infection.

Breast-feeding is permitted -- herpes is not transmitted in breast milk -- as long as there is no skin infection on the breast or chest. DPT Follow-Up

In answer to a question about whooping cough a few weeks ago, I mentioned that short supplies of pertussis vaccine prompted a temporary deferment in the vaccination schedule. But Connaught Laboratories has now resumed widespread vaccine distribution, which it had suspended since last July because of concerns about liability insurance coverage. Until the end of April, only one company, Lederle Laboratories, was distributing the vaccine.

Children can now be vaccinated against whooping cough, generally along with diphtheria and tetanus immunization (DPT), at the usual times of 2, 4, 6 and 18 months and 4 1/2 to 5 years.