Totally normal. I don't have any friends any more at all, you're lucky you've still got a few left!
Once you get pregnant and have a kid your priorities and interests change big time. YOu want to talk about milestones, breastfeeding, and babyhood (or swelling, navigating a huge belly, and general discomfort if you're still pregnant), and they really just don't give a caca outside of cooing over the cute baby and moving on with their teenage life stuff.
Not to mention, your friends will still hang out and talk all the time when you're in iwth the baby. They get used to you not being around.
Sorry youre having a crappy time. Sucks eh?
How old is the kid? Any chance you could join a mommy play group or something just to get out and be social?