I'm weaning my 15 month old. He's down to one feeding at night. Whenever I try to skip the feeding I get very sore. Breast infection?

See your doctor. Problems like these can only be correctly handled by your doctor in person. He/she needs to listen to you, perform an examination and possibly run labs or other tests. That's the only way he/she can find out what's going on and what to do about it.