A little upset about my relationship

I'm a teenager. I found a boy I really like and it hurts me to love him. I love him so much and usually he is such a good guy but he does stupid things that hurt me so much. I still always forgive him because I'm in love with him. I hurt while I'm with him but I have awful days without him. Yesterday he went out with his ex and didn't tell me about it and he's going out with her again and still has neglected to tell me (I know this because I have them both on snapchat. The girl has been posting him.). I am not an unreasonable girlfriend. I do not mind if he hangs out with other girls or even his ex but I want him to tell me about it first so I don't have to find out from something else. Comments please!