I don't know what to do

So I had a brief affair last year that ended the very end of Sept. Came totally clean with my husband and started working on myself because I really needed it. Things were really hard for four months. He would barely talk to me. He started warming up the beginning of February and we started acting like a married couple again. Sex, cuddling the whole nine yards. Things were going well. Last night Easter, I was watching baseball with my husband and my dad when the doorbell rang. My husband answered the door and it was the other man. He was acting really strange and said he was just in the neighborhood and wanted to say hi. Just really freaked me out. I am surprised my husband didn't beat him to a bloody pulp. I can tell he wanted to. Now things are rocky again with my husband because he doesn't know why this guy stopped by. I don't know why he came by. I am totally freaked out and don't know what to do. Need advice. Why did he come over. What does he want.