My boyfriend has had poison ivy for about 4 or 5 days now, the rash is on the bottom of his penis belly. Is it okay to have sex still?

No. Poison ivy on the penis is unusual. Only skin that touches a poison ivy plant or something contaminated with the plant oil would cause this. I suggest sending your boyfriend to the doctor for a checkup. In the meantime, wait on sex until his doctor says he does not have anything contagious.