Need Help

My boyfriend is sweet and kind and we have been dating since april 20,2007 and this person i know doesnt think he is right for me she thinks i should date her brother i have before and me and him only dated for 5 days well me and my boyfriend broke up april 23,2007 and we got back together april 27,2007 but he is scarded to tell my friend because she was trying everything she could to brake us up. But I cant keep this from a friend is that wrong. My friend just turnt 30 years old i hang out with her kids and i am only 15 her brother is 18 and my boyfriend is 17. My boyfriends name is steven i told me friend brother that i was going to go out with steven and he got depressed because i wanted to date other people. My boyfriend steven works everyday and my friends brother tryied to work but he wouldnt get up for work and i dont like him. But i still have feelings for him but i want to be with steven and all i talk about is steven i want to give my friends brother another chance but then i dont, I love steven and i never loved anyone else before besides family but the feeling when i am around steven or talk to him is amazing. When i am around my friend`s brother its like I am being burned. Please help me i dont know what to do or who to choice. When i first meat steven all he wanted was head but then we got to talking and he likes me he said he was sorry and he doesnt feel that way anymore. How can i tell if he is using me