I am experiencing rectal lump and rectal pain. When I lay down I have pain near the tailbone?

You may have abscess. You may a pilonidal abscess or a thrombosed hemorrhoid. If the swellinig is at the rectal opening then it could be blood clot in your hemorrhoid or perianal abscess. You may require drainage of the abscess. If your swelling is over your tailbone it will also need drainage.