What Causes Swelling And Pain In My Elbow?

I am curently takeing a blood thinner (lovenox) i have had several blood clots in my lungs and head since my diagnosis of b cell lymphoma in december. when i awoke this morning, my right elbow was swelled and verry painful: i dont think i bumped it,but cant be sure in my sleep. it has continued to swell and get more painful as the day persist. i am wondering if internal bleeding is possible?