I have a slightly mardy hip that I've never bothered to get investigated - GPs just take one look and say "you're too fat, lose 5 stone and then we'll consider looking to see if there's anything else going on" for that kind of thing, in my experience. I never learnt to do front crawl as a kid, but used to do miles and miles of (shockingly bad, as it turned out) breaststroke when I actually had a local pool to swim in - and would sometimes find my hip played hell after a long session in the pool. One of the things I had promised myself a few years back when I got a full time job in school was swimming lessons so that I could finally learn how to do crawl - so I found an adult improvers class at the not-very-local-at-all pool, and did just that.
I massively improved my breaststroke (to just-about-competent) and more or less got the hang of 'fly. I honestly thought I'd never crack front crawl though, as it isn't my natural stroke at all. I mastered 2 full lengths of full stroke 'fly (when 7 months pregnant!) before managing 2 lengths of crawl without stopping. But I got good enough, eventually, to be prepared to swim crawl in a public lane swimming session, and with a bit of work got reasonable enough to make it to about a dozen lengths at a go before having to resort to a couple of lengths of breaststroke for a breather!
Crawl was a _lot_ easier on my dodgy hip - and lets you swim more miles, more energetically, for less time investment IME. Would it be worth investigating if there's either a class, or an instructor that'll do a few 1-2-1 lessons, so that you can improve your front crawl and possibly swim more with less potential for hip issues?