A girl texted his phone and now I am questioning everything he does

The other day me and my bf were hanging out and his phone was connected to my car and some girl text him. He said it was someone he use to talk to last year before me. Says he hasn’t spoken to her since November, but she does text him on and off. He said the text said “I hope you know how hard it was for me to get your number and all I had to go through for it”. He said he doesn’t reply and that he blocked her. He said he blocked her, but now I just do not trust him. Ive been making snarky comments about it unfortunately and he just act like he doesn’t care that I am bothered. I have been thinking about us not talking anymore either because the first time I get the thought of you cheating/talking to someone else I am OUT. I have been through that enough! Am I wrong for being upset and not trusting him?