I think my Boyfriend is keeping contact with his Ex!

So, it's pretty much simple on my Birthday my Bf was so sweet to me he gave me a surprise gift in my house and after few min he called me by the name of his Ex ... I was like Wtf 😳he apologized immediately and felt sorry and he told me how much he loves me and how happy he is with me ..: but but it happens again in the same week but this time I was at his house and Seriously I don't know was going on I left his apartments very upset he says he really sorry it was an accident and I asked him what's going on and he says was because her birthday was coming up too and the date pops up on his phone 📱 so I said oh her birthday how cute .. so I don't know what to do I feel like I can't trust him.. and also he doesn't work on Wednesday oct 19 (ex birthday ) but now he's going to because some of his coworkers asked him  to cover him that day and I was like what a coincidence... what should I do ? I don't want to be paranoid or too jealous 😒