Please help me everyone!!!!?

My boyfriend is a big Flirt and he said to me that is not a flirt, he just try to be friendly and nice with everyone so my friend just help me to test my boyfriend by texting him through facebook and he failed. Although from the beginning when they text, he already admit that he has a girlfriend and he love his girlfriend, but he still flirt to the girl so much. after two days texting,My friend ask him to send her his penis picture. At the begining he didnt want to send because he was scared but after that when my friend said she will send her naked photos if he send. With some more persuading, he finally send it and he ask for her picture with whole body, boobs, vagina and ***. But my friend created a reason then she dindt have to send it right away. He said to her that she made him feel very horny. That's why she try to ask him for sex and he agree immidiately. After that, my friend ask him has to leave me so she will let him have sex with her but my bf realized that everthing was very fast and he said he still love me. My friend tried to convince by saying that he didnt really love me, he should break up with me but he said no, he just made a silly mistake, felt regret and he dont want to do it anymore.

I dont know if im a stupid to test my boyfriend so now I dont have to be sad like this. I'm so dissapointed. What should i do now, tell him the truth and break up with him or just give him a chance because at the end he already recogniz his mistake. pls help me!!