Is there something between my boyfriend and my good friend? please help!?

Okay this might be kinda long but trust me you would wonder what to do if you were in my situation. Ive been with my boyfriend for about a year now, but the reason y we met is because i was friends with his younger sister so i used to come around alot, around that time i had a boyfriend, but he was a complete jerk. So everytime i would come around to visit my friend i would see my elliot (my boyfriend now) and i was never quite into him i guess cause i had a boyfriend at the time, but we would talk and chill, and we would all be drinking together so we would end up flirting and messing around. After awhile, i stoped coming around for awhile and one day i came when all of our friends decided to go to the fair together, and I guess since my Good friend Susie( ive known her for about 4 yrs) was our ride she was asking everyone who and who was going, and she asked elliott if he wanted to go and he took it as she was inviting him to go with her and he began flirting with her, and it didnt really bother me. when we were at the fair he was all over her and he gave her a piggy back ride and took her to buy a funnel cake, she seemed as if she had a crush on him, but who knows. We all had fun that day but when night came and we were going to our cars i seen him them holding each other and she gave him a kiss on the cheak, i remember at that very moment i felt it really start to bother(i think thats wen realized that i really liked him) me but i never said anything.after we went home the next day i was hanging out with friend susie and i asked her if she liked him, and she said "not as a boyfriend"( now im not sure if she said this cause she kinda knew that we would mess around way before they went to the fair together ). she also mentioned that he even tried calling her a few times after the fair but that she wouldnt answer. So after time went buy she would stop coming around and only i would be around, we ended up talking more, and we ended up liking eachother more, we are now together and have been together for 10 months, everytime i would bring up the situation with my friend susie, he would metion that he never liked her, when i know thats a lie cause susie had also told me that at the fair he was telling her "i liked you ever since u started coming around, i liked the way you were goofy and sweet".... NOW, everyone heres where the ????marks start coming in...My brother was coming to vistit from iraq(army) so i decided to throw a party for him, my friend susie alowed me to thow it at her house, i had friends over and my brother and sister were there also, i had bought alot of drinks for everyone, that night i was so into talking with my bro after missing him when my sister metioned, hey i dunno wuts sup with your BF and susie but they have been by the sterio for awhile changing music together now i dunno if they are both drunk or wut cause they hav both been drinking but he keeps on following her everywhere she goes, i was so heated when i heard this, so i took my bf to another room and i put him in his place telling him wut is his prob flirtting with my friend, he just mention that there was nothing going on that i was trippin. i then took my friend susie to another room and confronted her and asked her wut was going on, she mentioned that there was nothing going on either but that he was playfighing with her changing the music and that he kinda did have his finger on top of hers wen they were changing the music. she also did mention that he would follow her around but that she would just end up walking away. now i was pissed about this whole situation, and me and my boyfriend talked and i mentioned to him that if her ever pulled that crap again that i would be out, i asked him are u Sure you dont hav anything with my friend and he says no...everytime ithink of the situation it bothers me and makes me sad, exspecially because i will feel uncomfortable hanging out with my friend susie when my bf is around. Wut do you think about all this How should i get over this, wut would you have done?