My friend died and his girl is having sex with his best friend. Should I be angry?

I have known this guy for awhile (Sam). I helped him through his problems, he barely knew me and would call me up and cry to me about his problems and of course I was being a friend and helped him. Then we became closer, but I was hesistant on hanging out with him cause he was always trying to have sex with me and I thought that maybe he just wanted to hookup and I am not that type. He seemed to really like me and such. We have only gone out a couple of times and it was with friends, like group settings never one on one. I rejected him a lot to when he would ask me out, cause I was hesistant, and he still talked to me and was cool with me. Everyone told me to stay away from him but I listened to him instead of everyone else. I found a good person in him and I thought to myself "Nobody understands him cause he had a bad childhood that is why he has a tough exterior" and so on. Well my friend Mikey died a August 8th, and I was friends with Mikey. and Sam knew Mikey for a year but he was very close with him. I was very close with Mikey as well since I knew him longer. Well I always had a thing for Mikey, but he got a girlfriend, so I figured I would keep it to myself what I thought about him. His girlfriend I didn't like. She was rude, bossy, and acted like she was better than everyone. She didn't fit Mikey, cause Mikey is so kind, warm, and caring, and she was controlling and bitchy. I figured though the relationship won't last, but when he was going to break up with her. She trapped him with a baby so he stuck with her. I supported him though and moved on, and I tried to be friends with his girlfriend. Well I noticed Sam was acting weird with Mikey's girlfriend (Leah) Before Mikey died they were hidden innuendos and I let it go.

But when Mikey died I was grief stricken and sick, and since Sam was close to Mikey too he was there at the layout, and he said to me "I wasn't even going to go, but Jessica said Please Sam Mikey would want you to be here, please come" I thought that was weird cause why would you care if Sam is there? Your boyfriend is laying dead in a casket and you just care if Sam is there? My mind was on Mikey and Mikey only I didn't care who the **** was there.

Then they were flirting with each other and such on Facebook, and I could just tell Sam and Jess were getting a little too close and this is days after Mikey died. I was in a depression for the whole month. I needed meds and therapy to get me out of it, and I am still in grief. I knew those two were getting a little too close, but I forgot about it cause I figured "Maybe she just needs someone, I won't look into it" Well it's been a month, but Sam texted me and said "I am onto something good here I will fill you in later" Well he never got back to me then the next night he texted me saying "What the **** are you doing? How are you? Haven't spoke to you in 2 weeks! Where you at?" I responded, but I forgot to mention what he wanted to fill me in on. Well it was just goofy texting, then the next day I text him here is the convo.

Me: Fill me in already lol
Sam: I would tell you who I am talking to but you have a gossipy ass household lol
Me: Haha, no I am secretive, I won't tell! :)
Sam: Jessica
(I played it cool)
Me: Jessica? I don't know who that is? There are so many Jessicas lol
Sam: I will kill you if you tell anyone, but it's Mikey's girl or whatever she is to him now
Me: OHHHHHH Jessica Smith lol
Sam: Yeah
Me: How long have you guys been going out?
Sam: We're not going out we are just talking
Sam: a lot lol
Me: Cmon
Me: Does she hang or bang? lol
Sam: Whattt
Sam: Woah. Easy.
Me: LOL I am just playin

That was the end of the convo, but I am furious, it's only been a month! He posted a pic of her and Mikey's baby that night when he said "he is onto something good" To me they both are grimey pigs. It would be one thing if she was dating random guys but ****ing your boyfriend's friend? And who knows how long they have been cause they were acting weird at the funeral. It just sickens me cause Mikey would never do that to Jessica, he treated her like a queen and she turns around and ****s his close friend, wow! And Wow to Sam too, he is a filthy, disgusting pig as well. I hate them both and I feel used by Sam cause I thought we were close friends, but he is just a pig. I also don't know if he is doing this to test me? to see if I am jealous or something? cause he was always trying to go out with me, but sorry for this long post I appreciate everyone reading, but tell me do you think I should be mad? Everyone grieves differently and I understand that, but they seem official and it only has been a month, and it's to his close friend! That is so gross and grimey to me. My heart just breaks for Mikey. Do you think that Sam is doing this to test me? Should I be angry? Thank you so much! Please comment! :)