This guy has no idea the future he is messing up. And yes, you should be concerned about stds. You may consider making him go to the doctor and bringing you a copy of his test results before you allow him to be physical with you. You may need to think about how you communicate to him also, especially if he's a "words of affirmation" love language person, for example:

When we make love, I really enjoy it because you put in a great effort (and I think your hot?); however, I'm VERY concerned that your extra marital affairs may bring in an std into our relationship, and that's not okay. So, I need your help to make sure it's safe for us to be together before we can be intimate again. I think you are a great husband and father, and I'd like for us to work together to make our life completely satisfying for everyone. Can you help with this?

Notice the "sandwich" structure of this statement:

<COMPLEMENT>
<ISSUE TO WORK ON>
<COMPLEMENT>
-------------------------------
<MAKE HIM PART OF THE SOLUTION>

This first part is called sandwiching:
http://www.nurturewithlove.com/conscious-loving-communication/

The second part puts some responsibility on him. He needs to be part of the solution, and really can be. Guys are built to fix things, let him do it. He can fix it; however, if he won't, then you have some tough decisions to make.

Praying this works out for you.

FunDad

Me:40
W:39
M:Dec 95
Split: Jul 14
W Filed: 9/16/14
Several Children
(including adopted)