This is potentially it. If you are a novice lifter, three days of lifting a week is plenty.
Why?
Because you central nervous system is not up to much more than that unless you are unusual. And strength/swole training is as much about your nervous system as your actual muscles.
So accept your new beau swiped left for your as-is state and wind yourself back in for a bit.
Or ditch the "new partner exertions" and get at least 8hrs sleep a night, whilst eating everything you see.
And for the love of all that is holy: if you can't do a single chin up you don't deserve to improve your bench.
I think you misread, I've just come out of a relationship, not just entered into one. Chance of "new partner exertions" would be a fine thing at the moment!
I think you're both right though, its most likely the combination of over training, lack of rest and a distinct lack of calories.
For now I think I'm going to have to live with it for now, I'll cut back a day or swap a couple of days out for cardio but I can't do anything on the calorie intake front, as much I want my lifts to progress my main goal at the moment is to get back to a reasonable bodyfat %, get to a point where I'm happy with my base and I can build from there.
As always though, advice is appreciated even if a lot of the time I don't listen to it