Hi palacelotty exactly the same happened to me. My DD started sleeping better from about 6 weeks old, but I found it increasingly difficult to drop off myself, and in the end was barely sleeping at all at night.
I'm not saying this will be the case for you, but in my case the not sleeping was my first symptom of PND. I developed terrible anxiety and the lack of sleep just made it worse. Everyone used to say to me "oh, just sleep when the baby sleeps" or things like "it's so hard when the baby keeps you up in the night"... it used to drive me mad, as I physically couldn't sleep, even though the baby was sleeping. It was so frustrating.
It's good to hear you are going to the GP on monday, that is what I would advise. You need to tackle this early to stop it getting worse and worse. The GP may run through a questionnaire with you to see if you might have PND. You may possibly be prescribed a short term course of sleeping tablets or somethings anti-anxiety like diazepam. I think it's fine to take these in the short term, to help your body get back into remembering that it can sleep. But try and not take them unless you have to... maybe every other night... and start with a half dose. Honestly, it is scary how quickly you can feel you rely on them....
Depending on whether the dr thinks you are depressed you may also be prescribed anti depressants. It's up to you whether you want to take them. In my case they helped (once they had given me the right one). But don't forget all your longer term coping strategies and techniques to get at the heart of your anxiety - you could try getting a self-help CBT book like this one or there are loads of others on Amazon. It's important to get at the root of your anxious thoughts and try to work on solving them, so that you remain well in the long term.
The good news is, it WILL get better! Sleep deprivation is horrific (blimey, do I know that) and it clouds all your thinking making you believe life is awful and it will always be this way. I sleep great again now and love being a mummy again. You will get through this, I promise x