Use of Antibiotics may have changed your intestinal flora, causing leaky gut.

Your ulcers are triggered by consumption of foods you have problems tolerating.

Try eliminating all milk products and all Sugar from your diet.

WS

I can't remember the name but you can buy a skin regeneration ointment that heals ulcers even though it was not specifically made for that job, it needs to be a regeneration cream but the name escapes me but I helped an old lady heal her huge leg ulcer with it when doctors could not heal it, I just got it from the pharmacist. Not all skin regeneration cream is the same, speak to a pharmacist and you may have to try more than one to find the right one but skin regeneration cream was brilliant and healed the old ladies leg ulcer up really quickly.

Im not sure if you eat meat or not, but excess consumption of chicken can easily do this especially as WS said if your gut flora is off.

I would do an elimination diet.
Do plain broth for as long as you can - ideally 2 weeks - then slowly add back in safe things - firstly something like yoghurt, and healthy fermented veg, if any reactions, take a step back, to broth...
just add things slowly. Be cautious of things like grains and try to eat with as little stress to the body.

Take note of the things that are stressful for it... for e.g., nuts with legumes might inflame you...

Your body is telling you your lymphs need a cleans...

The best supplement for this is called metagenics "Lymphatox" Its brilliant all-natural stuff. should sort you out. and other than that you could try a short Water Fast to clear up whatever current abscesses, use hot and cold compresses to rupture them, and then just go carefully back into plant diet, and DRINK LOTS OF PURE WATER... make it a rule that you drink 800mls before breakfast to flush, then wait 1 hr to eat... then same before each other meal..

I am of the belief that accesses are a spiritual ailment... but that is just what I subscribe to... I still treat them as described above...

Food for thought

All the best to you