STD TALK IN A MARRIAGE

Recently sat my husband down for a talk after dealing with infidelity issues we agreed to work it out however I just wanted to make sure we are on one accord and the goals for our marriage moving forward are the same..I recently thought that we should get STD  tested together and he agreed but I could tell he wasn't fond of the idea so I asked him his opinion on the matter and he asked why after all this time (we are high school sweethearts and been on and off for 8 years and married almost 2) during those off times he's been sexually active i on the other hand have not with anyone but him and he just cheated on me not too long ago!! So I'm wondering am I wrong for asking ?? Are they other couples that get tested together ?? Those dealing with issues and those who are not ????