Hi Beth, I'm 24 and have PKU, I know how you feel I was only ever allowed 6 grams a day. I found it really hard so went off the diet completely a few years ago, it did affect me in the same way as you, turned out I wasn't eating enough protein foods nor was I taking any substitue so I wasn't feeling the best. Recently I've found out I'm pregnant so have no choice now but to be really strict with myself. I'm only on 3 grams of protein a day which is hard! I've been taking lophlex lq for my substitute, they come in 4 flavours, berry is the easiest to take and I have to take 4 a day, you should maybe try them, I tried the coolers too but honestly I think these are easier to take. They're not that bad!