Defeated at the end of my rope

My SO and I have been TTC for 9 months now and nothing. I have 2 other kids from a previous marriage now 15 and 11 and it only took me roughly 4 months of "trying". Granted I was younger and am now 34 and my SO is 33. He has no kids of his own but is a heavy drinker. We went to a fertility clinic and both got tested for numerous things and everything was clear.

I'm so defeated and depressed about it at this point. I don't know what else to do or how to increase our chances other than the normal things. 😭