<human>: Give me the gist of the text in a nutshell

I don't know how to approach this to her family without it going pear shaped. I have mentioned it to her many times before and she agrees with me and has brought it up with her family. My girlfriend is in her last year of highschool and also doesn't have a job. However, the title is a very simple way of explaining it. So please read my post fully before commenting.

Basically I am in a long distance relationship with my girlfriend. Me from the UK, her from the US. We have been dating for over 2 years and have met up about 8 times (6 times me visiting her, 2 times her visiting me). Anyway, her family is pretty poor. I am by no means rich either. But whenever I visit her (which I am right now), I pay for most of the families meals and have done so for the past 4 trips. I justified it at first because I thought that they are letting me stay here while I visit rent free, including my girlfriend driving us around in their cars without having to pay for petrol. But it really frustrates me because there isnt much I can do about this from my point of view. 

My girlfriend cooks almost every meal in the house when Im not here. And obviously we can't eat out every night I am here. So I buy food for me and my girlfriend to eat. I usually have to purchase enough food for us to make which would cover her whole family (of 5). Now this is a tricky situation because I can't start to bring home enough food for just two of us and If I bring it up with her father then I might not be able to stay here the way I already do when I visit. I just don't know what to do. We buy and cook about 75% of the meals. Sometimes her father pays for them but usually if I am not here their diet usually consists of take out and fast food. 

Does anybody have any advice I can use? 

Thanks
<bot>: Pay for 75% of my long distance girlfriends families meals and am very sick of it as I have been doing it for the past 4 visits and I believe that this definitely shouldn't be my responsibility.