Hello,
It took DH and me 3.5 yrs to conceive - I am currently 23 weeks pg and just about finding some confidence in the fact that it is actually really happening.
I know what you mean about thinking you'll never fall pg; I can still remember the feeling of disbelief when I saw that second line on the pg test after spending so long just seeing the one.
We went through all the tests, tried 6 months of clomid and then ended up having IVF/ICSI because some issues came up around DH's swimmers (they were fairly lazy and not really that keen on going on an egg hunt
).
From all of the things we tried, I think you have a lot going for you. Success rates with clomid are much higher for people who don't ovulate naturally than for those who do where clomid is just used as a fertility boost. And don't be disheartened if it doesn't work in the first few months; I know tons of people who have fallen pg on their 5th or 6th month after convincing themselves that it wasn't going to work at all.
Also, you are still young so even if you do need to try something after clomid, you will have time on your side.
And the big thing is that you are getting help already; some couples I know left it until they had been TTC for 2 or 3 yrs before getting checked out and that just delays everything.
I felt a tremendous pressure to "stay positive" and "visualise it happening for you" and I remember that making me feel quite sad because I felt like my rubbish attitude was getting in the way because I simply couldn't believe it was going to happen for us. Personally, I found that accepting how I was feeling and letting myself wallow when I needed to was far more helpful than constantly maintaining a bouncy happy front when I was feeling like all I wanted to do was have a good cry and scream "why???" into my pillow before indulging in some wine.
Also, FWIW, the clinical lead at the hospital where we had IVF said to me that, in his experience, when people are getting help before they are 37, it is question of finding what will work, rather than worrying about if it will work. I felt that 37 was a bit of a random age but that's what he said!
I also wished that I'd been a bit kinder to myself as I know the whole journey really rocked my confidence in myself and my body and I think, knowing what I know now, I would have treated myself a bit more to things that made me feel feminine (massages, facials, generally pampering) to counteract how draining I found the constant let downs.
New shoes were very helpful in perking me up though 
It is definitely worth persisting; the Drs can do amazing things nowadays and there is every chance that this will work out for you.
On the plus side, I think because our TTC journey was so long, it has made being pg much more manageable; friends of mine were really down about morning sickness, aches and pains etc etc but I just think the whole thing is miraculous and that's kept me really upbeat even while hurling into the nearest loo on a regular basis, weeing every 2 minutes, and not being able to eat anything but salt and vinegar crisps for the first trimester.
I also have a pretty strong sense that our little person already knows how much she is loved and wanted.
Anyway, sorry for rambling, I just wanted to share my experience and to say that long term TTC and / or assisted conception does and can work!
Look after yourself and do rant on MN whenever you need to; the support I found here was amazing and really helped me through it all,
xxx