clw-
regarding mr. clw's std test, i would recommend that you ask mr. clw to give his doctor permission to share the results with you. i wouldn't take mr. clw's word for what the results are.
and regarding you taking an std test, you have a child with him, so you certainly have had unprotected sex in your past. therefore, it would be prudent for you to have a test also.
you are assuming that this affair is a one-off thing. perhaps it is. perhaps it isn't. he's already lied to you, so you would be wise to err on the side of caution.
naive