Thank you everyone for your replies, I am very grateful.
I should have mentioned re. kids... she doesn't want children and neither do I, so that's not really part of the issue.
I'm not sure what to do. It's hard, but she is a very difficult person to be around at times. There are times where she is lovely, she is very affectionate, funny and a kind soul. But very often she is distant, cold, and barely speaks. She is a good person - loyal, trustworthy, but sometimes she is just so cold and distant I feel so awkward around her. I don't know what to do about this.
I've had serious mental health issues in the past, and have managed to cope well for the most part. However when I have flare-ups - I'm having one now... she is not always sympathetic. She doesn't understand anything about depression/anxiety, so she provides very little comfort at times.
My plan I've sort of come up with is to try and communicate my needs better. I'm not very assertive and that needs to change. I think if I communicate my needs clearly, and she responds badly, I guess I know things may not work out. Today we had a nice day, went for a nice outing etc. but she was cold and aloof at times. It makes me feel so sad. I try so hard but nothing makes her happy.
Right now I just feel so anxious and tense, it's like my chest is going to explode. I'm trying to hold myself together but I'm struggling.
We don't live together, she has never wanted to stay at my house. If marriage is on the cards... we have to be able to compromise and ultimately live together for it to work. She has agreed to stay over at my house tonight - I'm pleased with this, but I still feel like I'm hurting. I don't even know why.
I'm sorry I'm rambling and don't make sense. I just don't know what to do, and I feel terrible.