baby won't stop fussing!

Kaila
My son is 2 weeks old and since we have brought him home he doesn't really cry. Might just get a little fussy when he's hungry but that's it. Breastfeeding lately has sucked it was so painful so I tried to pump and wasn't getting much, after feeding him that if he was still hungry I would give him formula. Sometimes I was only giving a formula bottle because I didn't have any pumped. After I feed he has been getting really fussy and gassy. I've been giving him gas drops but he just seems so uncomfortable. More so when it's just formula but still when it's breast milk. Tonight I haven't been able to get him to sleep. I feel like he's ate a lot. I gave him formula this evening and he got a little diarrhea so I went back to putting him on breast. But once he seems like he's asleep and I put him down he starts fussing again. I tried a pacifier and it helps until it falls out. He almost seems hungry but he literally just ate and it wasn't too long before that that he ate again I don't want to over feed him and make him sick. Any tips?