Hello and welcome (back) to everyone.
lucy Have you been told why you are on Clomid? There's another Clomid thread on this site that has had a lot of input from ladies with all sorts of different reasons and situations: here.
There could be many un-tested reasons why it's not working for you. I wish I could advise you, but I'm no expert. The only thing I could really advise is reading the other thread and finding out what other tests can be done with you and your DP.
Oh, I just noticed that you're not being monitored. That's not good. You should, at the very least have a CD21 blood test to check that you have ovulated. They should never just bung you on 6 months of the stuff and leave you to it! I've just taken 2 cycles of Clomid. They were prescribed by my GP, but shouldn't have been. I wasn't monitored, and the worry that caused me has been unbearable. Is there a different clinic you can go to nearby?
IVF is not your 'only' option, and it may not be that to get (long wait, fobbing off, etc), considering you have one naturally-conceived child already. Was s/he conceived with your current partner? Anyway, there are different drugs to take, lifestyle changes to consider, IUI, etc.
Read as much as you can about your symptoms. Perhaps you can suggest some more tests to your consultants. They aren't doing things right. Nag them for better monitoring too.