I have severe abandonment issues/trust issues. Most nights I dream of him and 100% of these dreams are of him cheating openly and saying he never loved me. We have been together for 5 months.
So I've been feeling a storm of emotions tonight. Last night, I asked my boyfriend about his past romances. We were just talking and I was curious so I asked. Well, he told me his most recent ex's name and showed me pictures (I asked what she looked like) that she had on Facebook. So they're still friends on Facebook, no biggie. So, he told me a while back that he cheated on his ex-girlfriend for his last girlfriend, which is this girl. Apparently him and the first girl were always fighting anyways and he felt so guilty that after a week or two, he came clean to both of them. He kept dating the girl for a few months but he had to leave to Australia so they broke it off. There seemed to be some inconsistencies to his story but I was scared to press the issue because he kept going 'why are you getting so obsessed with my ex's?!' even though all I did was ask about them once.
So anyways, I was on the bus today when I decided to check her out. There's a feature on Facebook where you type in two people's names and it shows you their interactions (tagging, posting on their walls, etc.). They haven't spoken since a few years ago except for his birthday last month. She just wrote the generic "happy birthday


Today I used the emoticon ':$' on him and asked if it meant blushing. He said 'Yes', plainly and simply. It just really upset me that he would send that to her, when for everyone else he just says 'Thank you

I'm terrible at controlling/hiding my emotions so I gave him the cold shoulder when he messaged me today and I didn't want to go over there and see him tonight like I promised. I feel like I should tell him this bothers me but am sure it may push him away.
Should I tell him? Is what he said something I have a right to be upset about?