I've had spotting before AF since MC but never really had it before that, even when my endometriosis was at its worst. I think it's more a case of some women get it, others don't and not necessarily to do with the disease.
Diet-wise I have almost completely cut out caffeine and alcohol and have tried to cut back on sugar as much as possible.
Anti-inflammatory foods include tomatoes, olive oil (not cooked, just over salads and stuff), oily fish (salmon, tuna, sardines etc), leafy green veg (spinach, cabbage, kale etc), nuts and berries and citrus fruit.
Anyone else like me who sometimes struggles with bowel endo or has endo sitting on their bowel it's really important to eat lots of fibre too to make stools nice and soft so it doesn't hurt as much when the bowel is working. As we're TTC, cereal with lots of fibre and added folic acid is a good idea to start the day with.
Other stuff I heard are useful are:
Tumeric, pro-biotics, valarian tea, and any foods which contain zinc, magnesium, vit B (folate, B6 and B12), omega 3 fatty acids and vit C.
Just be careful you're not taking too much of anything which can have an affect on a new pregnancy.
Basically the old adage of eat a well balanced diet and not over-doing it on unhealthy foods. A Mediterranean diet seems to be a good place to start.
And as someone else has already said, embrace the pain, just learn to live with it.
I was doubled over in pain sometimes and forced myself to go to a yoga class the first day of my period years ago, not expecting to be able to even stretch my legs out and I pushed through the pain. The rest of the day I only had mild period pain and I was amazed.