Boyfriend cheated?

Today I noticed a MASSIVE hickey on the right side of my boyfriends neck, close to the front. I have been very careful of my hickey placements and usually do them toward the back or somewhere hidden. I also swear that if I would have given him one it would have been on the opposite side. I asked him about it and he said that I gave it to him on Monday. He also said that him carrying baseboard may have made it bruise (he’s been doing baseboards for 2 years and this has never happened?). Then when I asked him about it later he said “I don’t know what to tell you baby, it’s kind of annoying that you don’t believe me”.

I have no idea what to think right now. Any ideas?