We need your ages to even have a clue what is wrong.
i will admit i gained a few pounds after i moved, i have a thyroid condition.
How does a thyroid condition prevent you from exercising? If you say you gained "a few" pounds, that means you gained a lot more than a few.
have tried [talking to him] a bit....but the convo doesnt get very far before he brushes it off as a minor issue or we get interrupted by kids or something else
You let the convo get interrupted. Set things up so you two won't get interrupted. Be more proactive. Send the kids to a neighbor's or relative's house for 2 hours. Then have your conversation in a private place. If he's having ED troubles, many men are embarassed to talk about it. They never used to have trouble getting a boner, now they do, and it's a VERY big change to them, which is hard to deal with. You need to just ask him if he has trouble getting an erection, or if his libido is zero. Make sure you say you love him and accept him even if he is having problems.
Heavy exercise will help libido (I'm there myself). Meds can help ED.
I have a long time interest in psychology, specializing in relationship dynamics for 30 years.
(Please note, we give the best advice we can based on the information given in a post. For better advice, please include the age of all romantic partners.)