I've had it for 17yrs and it is a big deal. Have you asked your GP for a referral to see a dieticia? Food advise for ibs-d and ibs-c symptoms can vary to opposite ends of the scale e.g. ibs - d you might be better with foods like white bread, fresh pasta, avoid some fruits and fruit juices, avoid lentils in soups and ibs - c sufferers may cope better with wholemeal bread, weetabix, brown pasta, hearty lentil soups.
I've seen low fodmap mentioned a lot recently and considered it myself. It is very restrictive and complicated and your body might not actually need to restrict so many foods. There are specialist dieticians for fodmap but life will be easier if you can cope with the basic restrictions before a low fodmap diet.
Some of the basics to try until you see a dietician (if you decide to do so)...
google gas producing veg and avoid these.
Drink lots of water, herbal teas, avoid drinks with caffeine.
Avoid anything with artificial sweetners (this pretty much includes all sugar free/diet options).
Dietician told me to try a spoonful of golden linseed in food for 4 weeks to see if this helps OR Yakult for 4 weeks.
Don't reheat already cooked carbs (takeaway rice, toast, frozen potatoes, potato scones, toasted muffins etc, pizza base).
Stress management is also a biggie for ibs but difficult to get through life with no stressful periods.
Like you my ibs seems worse at certain times of the month. I've also really struggled with alcohol to the point I'll drink only a couple of times a year now instead of every weekend. I tried gin and full fat tonic for the first time last weekend ,as I seen somewhere that this was low fodmap, and I was okay while I was out! Still struggled the next day but I'm sure this was just down to quantity. Huge progress!