Is there a link between constant fatigue and serotonin levels?

This may sound like a dumb question... But I really am unsure. What is the difference between a milk allergy and lactose intolerance? Or are they one in the same? I was in an accident when I was 14. I had emergency surgery on my liver and spleen. After about the age of 20, I have developed severe mad dashes to the restroom after eating anything dairy.

But I have a lot of sinus allergies... that seem to flare up after eating milk products. Although generally milk products do cause thickening of the mucus... I was wondering if severe congestion also goes with it? I no longer eat milk products, of course. But I recently read about a child with a milk allergy who could not breathe through his nose afterward... accompanied by severe coughing. I am now 40 and learned my lesson well... But still curious and always looking for additional info and answers!!

During sex, my husband likes to squeeze and suck my nipples. I enjoy this, but am worried that this type of pressure on the nipples may cause problems later on: we are planning on having a baby in a few years, and I want to breastfeed. Might the pressure of squeezing and sucking hurt my mammary glands and ducts, making it difficult or impossible for me to breastfeed?

1) I've suffered weird digestive things when I have my period. The way I have heard it explained in my MCAT class is that the same hormone that causes the smooth muscle of the uterus to contract unfortunately works on all of our digestive organs as well, particularly the large intestine. So that's how I've come to grips with the apparent confusion of the digestive processes during my period.

2) Does a person's menstrual cycle regulate her bowels in any way? I have had some problems. The week before I get my period, I have loose bowels and the week afterwards I am quite constipated. Is this normal? Is there anything I can do?