RedTearsBlackWings, I am new to this board and have no idea if you are following it anymore or not, but I feel that Rox was just trying to help. It is true you are very young, and very likely, many of the posters here have spent decades longer on earth than you have. I say this only to introduce the idea to you that when you have spent more years on earth, you have more experiences to share with those who are younger. I'd wager that more than a few people on this board also know what it is like to have multiple illnesses/problems throughout their lives. I know that I do; besides IBS and colitis, I live with 2 autoimmune diseases that make life a challenge. However, you have to keep trying new things and not give up. To you this may sound ridiculous, but to those of us who are older than 19, we have learned that there is little else to do. Granted, depression and frustration are very real when one can't lead a normal life due to health problems, but my mom always says where there is life, there is hope, and you have to hold out a little hope.
I have also experienced pain and bloating due to waistbands on pants and skirts, and really all you can do is look for items that will be loose on you. A dress with an A-line design or an empire waist will be your best bet. I know that I buy pants in a larger size, just so the waistband will be larger. For me, the bloat gets worse as the day goes on.
As far as your heart condition goes, I really can't say I understand why in Australia they will not allow you to have surgery to fix the hole in your heart. My niece was exactly your age when they discovered she had one--they only found out because she had a stroke. She had it repaired surgically and she has spent years recovering from her stroke. It is not true that young people never have health problems!
Rox was right about physical therapy. A physical therapist is used to working with people who have multiple health issues that compromise the ability to move their bodies. Again, I don't understand why you can't access one in Australia. Don't you all have universal health care? That would cover at least a few visits to a PT. In any case, your best bet is to do some very gentle movement first and work your way up, even though this will take a long time and no doubt get discouraging. Keep a journal about your daily progress. That way you can go back and see if you have made slight progress. Something is always better than nothing.
I (and I'm sure many people on this board) empathize with your struggles. Life is not easy for everyone--no doubt about that. The human body is very complex, and for many of us, there are no clearcut answers, so the search for answers continues.