Mad At Me :(

So yeah, my gf is mad at me. ;o; we aren't official or anything, but yeah.
She's mad at me because I can't stay the night at her house and she said I'm being inconsiderate.
Her bed hurts my back really bad T.T She stays at my house a lot though, so I don't know what the problem is...you know? I mean, every time I go grocery shopping, I always buy her stuff she wants and leave it at my house and I don't touch it.
She likes Fruit Loops and nobody else can touch them except for her. I buy things for her that I really don't have the money for, but I do it because it makes her happy.

I mean, I do buy her stuff when I can.. last night we went out for dinner, and I bought her food. And I bought her lunch (plus I order for her bc she gets too nervous to do it herself) and I bought her candy and flowers, and I left her a long message for her to read when she wakes up.

The last few days she was like, "oh I don't mind buying you things bc you deserve it" now she's like "I gave you something now do what I want" like, no.. and she keeps telling me that she spent all her money on me. No she spent $25 on me, and I spent $110 on her this weekend.
So she's mad I can't stay the night. I really can't! I work two jobs and tomorrow I have my double shift and I need a good nights sleep. Her bed kills my back and my physical labor job hurts my back too.
I feel bad that she's mad at me. And she texted me and said "don't bother bc I don't care"

It's not just me. I'm not selfish or self-centered. I'm really not.
I play video games with her usually till 1 in the morning and I'm tired.
I don't even mind when she gets me an assortment of chocolates and eats all the good ones and makes me eat the crap ones left over. I never say anything, you know?
Like, she took a bite of one and it was strawberry and she said "eww it's strawberry! here, you eat this one" and put it back and took a different one.

She just wants to spend time with me a lot, and I want to make her happy. I don't like it when she's mad at me or upset.