Hello, welcome to the forum
I'm so sorry that your boyfriend left you, but it sounds like he's done you a favour. It's very hard for people to completely understand what this is like if they've never been in this situation but people can at least be supportive and your ex certainly wasn't.
I had some really horrible relationships before I met my finace, people who made me feel like being sick was my fault and didn't take me seriously enough when things were bad. It took me a long time and a lot of encouragement to realise I deserved better than that.
In terms of your symptoms, are you taking regular medication? It might be that they haven't quite got the dosage right or you may need a totally different treatment plan. They can also do lots to try and help your symptoms including medications to slow down your bowel movements.
You may have already tried this but it could help if you keep a food and symptom diary for a week or so, write down what you're eating and how you feel, and see if your symptoms are worse after specific foods. If you find that certain foods consistently make your symptoms worse, you can cut them out for a while.
There are so many people here who understand what you're going through and can really relate to what you're feeling. Everyone here has been in situations like yours and we all know how lonely chronic illness is, but there's no need to go through this alone. Any time you need to talk, or have any questions, please come and post here. There's no need to feel embarrassed as we're all in the same boat and there's no question too small. If it would make you more comfortable talking to someone one on one then please also feel free to send me a private message. I'm only 25 myself and was sick throughout my teen years, so I can really relate to your situation.