Hello, I am a 43 year old gay man.

I've had the same sexual partner for about 15 years now but I have suddenly developed what looks like cystitis. I'm a bit worried as I've tried to cure it at home with medication (ibuprofen) and loads of water for 4 days now but it is still very painful to pass urin and I do not know what to do. Has anyone had the same or a similar problem? Should I be prescribed something stronger at this point? It is disrupting my everyday life and I've recently been under stress but can this be really the cause of it?

Thanks.