I struggled with some of those same issues when I was a teenager. I have had ITP since I was 8 years old and I'm now in my 40s! When I was your age the only medication option available to me was Prednisone. I can look back at photo albums and very clearly see the times when I was on higher doses and had my moon face. It was a struggle at the time for sure, but you are fortunate to have some other treatment options available to you that weren't around when I was a teenager.
If you are feeling lots of anxiety and depression as a result of your treatment, please talk to your doctor about some of the other options. I'm trying Promacta now after bursts of prednisone lost their effectiveness when I got older. Things are going fairly well and I have no noticeable side effects.
Don't feel that you lack other options and please talk with your doctor and let him/her know that you are having trouble being on the steroid. I hope you can find something that works better for you.
And as Sandi so rightly pointed out, you just want to have safe platelet counts, not normal platelet counts. I've lived most of my life under 70,000 platelets and as long as my counts weren't especially low I've been able to enjoy a normal quality of life. Don't shoot for 150,000