Can I take tylenol (acetaminophen) during first weeks of pregnancy to relieve cramps? I have period like cramps on one left side of abdomen and lower back. Normal?

Medication. Of course. But, cramping is in no way a sign of pregnancy. Remember that at one week the mother does not know a new baby has been created. There is no communication between new impregnated egg and mother yet. That would be impossible.