Low testosterone?

This is our first cycle TTC and so we have been trying to have sex every day. Before now we usually had sex 2-3 times a week. Now with doing it almost every day it’s been taking him longer and longer to finish and this morning he wasn’t able to. Our window is going to close soon and I obviously want to give ourselves the best chance of getting pregnant but I don’t know what to do in this situation? Is this normal? Could he have low testosterone or another issue? Help!