7 Week Old Wetting Through at least 4 times a day/night - any suggestions?

[ScaredyCatMum]

My 7 week old is regularly wetting through his nappy and babygro (sheets, etc.) - probably on average about 3-4 times in 24 hours. We're currently on disposable nappies but awaiting a trial pack of real nappies we've ordered. We're using Pampers and have gone up to the size of which he's in the bottom weight of (if that makes sense), which seemed to help for a while, but now he's wetting through them - 3 times since 10.30 last night at latest count. Although he's only 8lb 15 oz, he is filling the length of his 0-3 month babygros, so is long and thin - which may be contributing to problem.
Anyone else had this experience and found any good solutions? It's not that I mind changing him, but that I think this wakes him from naps/overnight sleep, when he would otherwise sleep on and he is therefore not getting as good quality sleep.
Someone suggested to me the other day that someone going to loo more is actually dehydrated rather than over hydrated - cue me worrying now about milk supply (compounded by only managing to express 1.5oz yesterday after 30 mins on one boob - second time of trying) and him not getting enough to drink, although he put on 7.5 oz last week and when I fed him this morning, I must have misread his cues, as he's consequently brought all of it up and now busy filling his nappy (so loudly I could here him upstairs and he's downstairs - sorry TMI alert!)
Any advice gratefully received.
Sorry for long winded post!

Hi, my wee one was long and thin initially (now rather chubby at 13 weeks!) and wet through her pampers nappies. tesco disposable ones were the best for her at that stage though now she's chubbier the pampers are great. I tried huggies too but found the tesco ones the best. they're bulkier than pampers but what does that matter at this age?!

I had the same prob with DS. A MNer suggested making sure that the willy pointed down, which made a big difference... It sounds like a 'fit' issue rather than a production issue, disposables can absorb huge amounts, don't worry about hydration.

Thanks Ladies - I will try the Tescos nappies oneweemite and keep fingers crossed. Thanks for tip bakedpotato - MIL also suggested this and we've tried down and to left as always leaks to right (guess we already know which way he dresses for the tailor when he's older !)

thanks for such quick responses!