My bowel movements always change

Hello I'm quite concerned, I'm 22 years old male with the following symptoms, my BM can go from loose/mushy (sorry for the detail) but the same day later on my BM could be what i would say a normal movement? And then I could have normal for a few days then back to that again. I have other symptoms but not sure if related, chest rash usually after eating but sometimes not. Neck tenderness but thick that is my anxiety feeling for lymph nodes bad I know. I've had post nasal drip for 5 months! constantly. And a coating on my tongue that can be scraped off but comes back within the day. Seeing a specialist next months, so anxious.

Keep a food diary in case the the rash is due to a food allergy.  Do you have any stomach pain that shifts about and changes in intensity and type?  Do you get relief of symptoms after a bowel movement and incomplete evacuation?  If you do, it may be IBS.  Ask your specialist about this condition.

I'll start a diary up. I have slight pain in the left very mild but noticeable, started after i ate out earlier today. First time i've ever had that.

Could be food related if it started after you had eaten

Seems like you have an overgrowth of yeast (candidas) in your body.  Start taking probiotics.  Eat a clean diet...no red meat, no dairy.  You may also have IBS (Irritable bowel syndrome).  A doctor once told me that Metamucil fiber (you mix with water) will fix both constipation and diarrhea.  Google how to get rid of yeast (candidas) in the body.  Hope you feel better soon.

thank you, had quite a few people on here saying it is candida related. Just need to get the diet correct.