Back story: I split up with my exH about 18 months ago. I have 3 DC, 6, 5 & 2. I met DP 10 months ago, all going very nicely indeed. Due to HMRC royally fucking up my TC in the summer & leaving me in a situation where I was earning less than my childcare costs, I was forced to give up my (much loved & fairly well paid job 
). I now live entirely on benefits & maintenance.
DP currently spends approx 3-4 nights a week staying over, most weeks his DD stays over too. We don't want to live together (yet)...too soon plus lots of other reasons. DP is very good about picking up whatever food we need for specific meals, milk etc whenever I ask & almost always pays for very rare takeaways or meals out. However, as you might expect I cover all household costs, heating, hot water etc etc plus providing all basic essentials (tea bags, washing up liquid etc).
Money is very tight for me. I often find myself penniless & have to borrow money from DP which I always pay back.
Would I be unreasonable to ask him to contribute something towards my household expenses? I honestly don't know. Have reservations where that might leave me from a benefits point of view too.