I'm scared my marriage is over

Back story- We have been married almost 16 yrs. We have three boys together. I have been wanting more for a long time. We decided to have a tubal reversal back in August 2016.

We thought, well it shouldnt take that long. Well here we are 17 months later and not one bfp. Found out two weeks ago that I have hypothyroidism. I'm taking meds for that but all we do is argue anymore. He picks at every little thing and it hurts to hear it all the time. We were great before all this.

I am scared that since its not happened that I'm going to lose him. He is struggling real hard with the fact that we're not having one yet and our boys are almost to the age of college so they will be leaving.

I don't know what to do. I'm so scared that I'm going to lose him. Can someone please give me some good advice?