During sex lately, I've been losing my erection when my partner becomes wet. Sometimes I feel like I am really close to ejaculating, but the lack of pressure seems to make it hard to sustain. More often than not, I don't climax. It could be that lately

I’d say you’ve hit it o the head with the tiredness issue. It’s almost impossible for anyone, male or female, to enjoy good quality sex if they’re overly tired. To do anything well in life you need to make sure that in you’re in a good state, sex is no different. So think outside the box when it comes to timing , there’s no rule that it has to be last thing at night – do it before dinner, straight after dinner, come home for ‘lunch’, or my personal favourite, the long Sunday morning lie-in.