aww man, sad to say it but its definitely the stress and sounds like the g/f is to blame.
not sure what to suggest because i dont know you or your g/f or the situation youre in.
One thing i know for sure is that love/relationships are supposed to bring happiness and take away the stress, not add to it.
life is too short and pointless to get stressed out, you have to work out exactly what is causing your stress and stop it spoiling your night times once and for all.
maybe before you sleep:
-have a long bath and read a book
-spend some time to think about your stress and clear it from your mind before you sleep.
-make sure your bedroom doesnt have anything that reminds you of work, stress, cats, etc. sounds silly but it really makes a difference.
-get stoned or have a little drink
-kick the cat outside and keep old shoes ready on window ledge. (optional)
most important!
- make sure you have had some 'Me Time' every day. if you have not done something that you want to do just for yourself each day, then there was no point in waking up at all. its your life, dont waste it on other people the whole time.
all this stuff helps me, i have had times of serious stress in my life.
all the stress is still in my life but i have found ways of not letting it bother me when i need to get some good sleep.
worrying about your stress will take years off your life and so will losing sleep, its just not worth it.