i can't get in the mood

For the past few weeks, anything sexual has just been a no for me.  My boyfriend tried to have sex with me and I just make up some excuse.  I try to watch porn and I can't even do that because for some reason all I can think is "Ew".  I'm horny, but I don't wanna do anything because everything is turning me off.  
**My BF can please me I just haven't been in the mood