I totally get that feeling. Its so frustrating knowing what you're capable of and just not being able to do it because the language you need to do it in is different. What makes it so difficult, i think, is that you worked out your style and the way you like to do it in English over many years, and style is just really hard to emulate across languages. Especially as grammar is automatically different, and vocabulary is usally so much more limited in comparison to english (did you know it has over 20000 more words than most other languages on this planet?)
Anyways, to strategies: maybe figuring out what your style is defined by in English, and then trying to find ways to do it similarly in swedish. For example, if you usually use slang in english, use slang in your swedish writing. Or if your description usually has longer sentences than other parts of your writing, try to keep that. It will make writing in swedish a little bit more comfortable, hopefully, because you get to keep some of the habits and things you enjoy.
Another thing I've seen bilinguals around me do (and have, admittedly, done myself) is just cave, write it in english first, and then translate. One danger of that though is losing the voice your narrator has/making weird grammar mistakes because of translating word for word. So if you do do it this way, just be aware of the pitfalls and avoid them.
I know it's frustrating, but hopefully these things might make it a bit easier/more fun. Oh, one more fun thing to do, is use all the weird sayings and euphemisms you can only do in swedish, just for fun. I mean its not like they'd be easy to integrate in any of your english stories, so its sort of like a cool opportunity ;)
Anyways all the best for your writing!
