Ibs suffers often have problems with internal hemorrhoids so this increase the likelyhood of your current issue being hemorrhoid related.
Until internal hemorrhoids become thrombosed many people do not even realise the have a hemorrhoid problem.
Over the counter treatments can help, but as you no doubt realise diet is also very important.
1. Try and consume fiber rich vegi's and fruit daily
2. Drink at least 4 to 6 good sized glasses of water a day
3. Make sure you chew your food very well before swallowing
4. At least for time being avoid heavy foods like red meat
5. Try not to sit for long periods of time, this will most definitely cause problems.
6. Use the over the counter cream as an internal lubricate just before and after a bowel movement
7. When you go to the toliet for a bowel movement, remove one leg from your underwear and sit with your feet apart