I'm 20 years old and for about 5 years now I've had awful bouts of cystitis, there isn't one day that goes by that you vagina doesn't sting just a little bit. I'm constantly at the doctors and they very rarely find anything in my urine. I've been given Trimethoprim on countless occasions but it never seems to do anything. I lost my virginity at 17 years old with my current boyfriend so have only had sex with him, he had sexual partners before me but has been checked a few times and is fine. The doctors did think I might have chlamydia but the results came back negative. I wish I could pin this all on sex but it was happening way before that so it doesn't. I have found that condoms can make the pain worse so me and my boyfriend rarely have sex as I'm in pain so often. I literally take cystitis cranberry drinks every day which do nothing either. When I get a bad bout of whatever this is I'm on the toilets every second, peeing just a tiny bit each time, hurts to walk, makes me feel really cold and just burns. Every day my vagina will sting but it's bareble. I use vagisil daily which sometimes helps and canisten which doesn't help, I take showers and not baths, I use vagisil soap...I've literally tired everything and I can't handle it anymore. I'm in so much pain all the time and the doctors don't help. Please someone help me, it's ruining so much for me and makes me really unwell!
I am sorry for so much pain. Have you thought of second opinion? There are medications that help with this embarrassing problem. Have you been prescribed suitable antibiotics for short or long term? If not, you can ask your doctor for same. Even surgery or bladder distension could help. If sex hurts, taking single dose of antibiotics after sex can also help. Avoid wearing nylon underwear and tights. I have heard, natural yogurt in the vagina could be effective too.
I'm really sorry to hear that. I used to get them all the time and still do occasionally, mine are because I have IBS, and get constipated easily. When I'm constipated I get UTIS.
have you considered talking to a herbalist? I avoid citrus fruits and eat probiotic yogurts sometimes which seems to help.
I drink 2L of water which has proven amazing for avoiding them. I avoid caffenated drinks and too much chocolate.
Your condition sounds serious so I would keep on at your doctor to be examined (I'm having an external and internal ultrasound next week ) and ask to be transfered to a urologist, hope this helps!
if you find anything that works or you have discovered an underlying problem then please post back!
Good luck 
In my mid 20's I suffered with this so many times (always after sex) and it was horrible. I have a good routine now though and I have managed to avoid it for the last 5 years. Here is what I do: I always go to the loo straight after sex, and over the next 24 hours I will drink a soluble 1000mg vitamin C tablet (which I heard makes things more acidic and harder for the bacteria) and later on I always drink 3 glasses of water over the course of an hour, so I go to the loo a few times to keep the bacteria from being able to multiply. Really simple but very effective for me. I really hope this helps someone as it used to make me so down suffering with it so regularly.