husband couldn't cum

So, we have been TTC our 2nd for 6 months. It was my husbands idea for a second child and he is wanting it the most. This month was the first time we had used ovulation tests after my husband had asked me to give them a go and got a positive test for ovulation yesterday so I told my husband that yesterday was the day. He was excited and wanted to have sex but when we came to having it he couldn't cum, we had sex as normal he just couldn't ejaculate. He then wanted to try again an hour later but the same happened again. He felt really embarrassed and fed up about it and kept apologising. Iv told him not to worry about it and it's nothing he should apologise for and said it may have been that he put too much pressure on himself. As anyone else been in this situation?