Why do I feel like something is going on?!

Sa

Alright y’all we all know a woman’s intuition is something serious. My boyfriend and I have been dating for a few months but we honestly were serious about each other kind of fast! He told me he loved me and was falling for me pretty soon I held back on how I felt but have since expressed it.. I am not an affectionate person at all but with him I am and it flows naturally. He was too at first but got a great job right after we started dating.. I’ve told him I’m falling twice in the last week and his response is something along the lines I feel the same and I don’t want to be without you but never I’m falling for you too etc. recently some chick liked his picture on fb he never spoke of her before but who cares he knows a lot of people he’s from where we live and I am not! Well the next day they add each other on IG and I just felt weird about it and went off he said it’s one of his friends ex girlfriends and someone he’s known for awhile (he’s 4 years older than me!) okaaaay. So I felt like a dumbass. But I can’t shake the weird feeling and I’ve been super stressed with school and taking care of my grandma who has Alzheimer’s. I don’t know if I’m being paranoid, letting my old habits come creeping because of my past or if something is seriously up! Please be kind or say nothing at all !