Ooh, you mean your permit expire
S in August, not that it has already expire
D. Big difference!

In that case, you should not run into any big problems with the paperwork.
I seem to recall from other stories here that it took about 4-6 weeks for the marriage paperwork approval. After that (or maybe at the same time) I believe you'll want to apply for a family reunification permit to stay here with your new Swiss husband. The authorities in Bern will be your best source for information on requirements and timelines.
Congratulations on your upcoming marriage.