Someone tell me what to do please?

A few days ago, myself, my boyfriend and our 2 other friends got into a huge argument that left us bothered. I feel like most of the argument hurt me the most because it affected my trust for my best friends and my boyfriend. See, what happened was that our 2 friends, (we'll call them Jose and Heather.), got into a fight earlier the day everyone went off. Jose had managed to go through Heathers phone and read information in her text and on her Facebook. After reading the information, he and Heather got into a fight and they stopped talking. Next, he calls me because he was mad at what I wrote to Heather. Their relationship, keep in mind, is an open-on/off relationship. So I told him my side of why I told Heather some of the things I said. So he agreed and brushed it off. Then he told me Heather was talking to my boyfriend in a manner that has me questioning my friendship with Heather and my relationship with my boyfriend. I knew earlier they were talking but it was strange since for the longest time my boyfriend hated her and vice versa. For them to talk like they been best of friends now is strange to us which was why it upsetted me and Jose. My told my boyfriend what Jose told me and my boyfriend got mad, saying him and Heather were just talking and nothing else. Later on, he came to pick me up from work and we drove to Jose's house with me crying in the truck. My boyfriend blew up on me because Jose's words were messing with my head and making false accusations yet I had known something was wrong before Jose told me. We eventually got to Jose's and my boyfriend and Jose got into an argument. The things my boyfriend was saying to him about me made me feel lonely, betrayed, naive and unloved to put it to point. I felt like he no longer trusts me and no longer cared. So I stepped out, crying and almost shaking hysterically. Jose told me to go stand on the sidewalk by the house. I didn't want to but I did anyways and because of this, my boyfriend got mad, got into his truck and sped away. Me and Jose went into the house where he apologizing for everything. He then calls Heather and tells her what happened. She gets on the phone with me where I tell her I made my decision of breaking up with my boyfriend who I been with for 1 year and 3 months. She told me to stop and that she will come over and my boyfriend will pick her up. I told her whatever but I made up my mind. They came and Heather pulled me aside to speak to me alone. She confirmed nothing is happening between them and that Jose was just making drama from what happened to them. Yet knowing her, I knew she had it for my boyfriend and has liked him from the beginning before he and I went out officially. Then she brought my boyfriend over into the group, telling him to listen to me first. After telling him how I felt (confused, a liar, scared, lonely, untrustworthy, abandoned, stupid, tired, abused, agitated), Heather told me to listen to him and hear him out. I heard him. He denied everything. Said he loved me and wants to be with me. Heather was pretty much the medium in this conversation and adding little jokes here and there not succeeding in making me laugh but it made him laugh and smile I felt (because I never looked to see him). After we were done, me and my boyfriend made up and her and Jose talked again, lead to yelling and Jose storming back into the house. My boyfriend took myself and Heather to 7/11 for late night ice cream and dropped me off first home. Ever since then, when I hang out with my boyfriend, I catch a glimpse at who he's texting and I see Heather's name which raises back suspicions because she wasn't talking to me all day. They been talking for about a month and she knows everything hes doing, what hes going to do next and I feel like she knows him better than I do within that month than me being with him for a year+. I told him this and he tells me I'm being jealous and that if this relationship goes down, its because of me and my insecurities. Though my feelings tell me I should be aware. My boyfriend has never cheated (for I am his second girlfriend ever) and Heather has. What should I do? Brush it off? Lose my boyfriend? Lose my friendship with Heather? I feel sick at times thinking about this. I just feel like I can't trust anyone. And its sad I can't trust my best friend and my boyfriend because I feel if she had the opportunity and he was weak, she would take him in a heartbeat which is sad cause I know she loves and to Jose still and her previous ex. What should I do? What can I do? Is it because I am now a jealous girlfriend or should I listen to my gut? I don't want to feel this way. And I love my boyfriend too much to give him up. I broke up with my ex-boyfriend to be with the man I'm with now. I don't want to feel like I made a mistake anymore. Just today, Heather asks me to go hiking with her, same time my boyfriend is up and talking to me as he goes to a doc