It not fair on me!!!! Upset!

Ok so today me an my boyfriend came over to my mum's place becuae I am looking after my sister while my mum works tomorrow, so when we got to my mum's, mum wanted to take me for a drive cuz I'm on my Ls, so before we left my bf said he was going to go out for a few hours with his mate, I said yer ok he said he would be back in 4 hours! He promised me before I left that he wouldn't text me saying he was staying out tonight to drink or whatever!

About 1 hour after he left I get a message from him saying hey babe, is it ok if I stay out? I called him and just got upset and said it's not fair you do this to me every time ! (Mind you I had a $250 surprise for him in the morning as a late bday present) so anyway i just got angry and upset! I have now also lost $250 because he wanted to go out! Am I over reacting? How would you lady's react? What do I do?? I'm really hurt by this, it's the 5th time it's happened in 4 weeks!