Yy to metformin. I didn't conceive on it (wasn't trying to) but it regulated my pcos symptoms and I lost stones. It took away my appetite so made my diet (slimming world) really easy to stick to as I wasn't munchy all the time. Pcos can play havoc with your body's ability to process insulin. Insulin, if unprocessed in the body, can play havoc with your hormone balance, making pcos worse, making insulin worse and so on in a vicious circle. If you can get one thing under control you often see dramatic improvement in the others.
Weight loss, even a little, can help conception too. When I conceived my ds, I had lost a stone doing low gi eating and walking to work instead of the bus. Im not an expert but I think it's got something to do with how you store oestrogen: I think it's stored up in fat cells, and when you lose weight, releases itself. Losing a few pounds can have an effect on hormones by releasing this oestrogen into your body. I literally had my first period in over a year once I'd lost my first few pounds.
It's really, really upsetting having pcos. And the condition itself can cause depression. What is your gp doing to manage your condition? You don't mention specialists or medications at all. You say you need to lose weight to get treatment but this should not be the case: the weight is a symptom of your condition. Yes, you may need to be under a certain BMI for IVF, but actually you need to see a reproductive endocrinologist and look into managing your pcos as a condition first. Just telling you to go away and lose weight is not helpful: you should at least have been offered metformin by now, and there are other drugs you can take to assist weight loss too. I got met from my gp, and then a referral to a rep/endo. Managing your condition is very important but you do have to be informed and quite confident about what you want. Is your gp sympathetic? If he's been letting you try for 3 years and hasn't even mentioned metformin, I would be looking for another gp with some expertise in your condition - I found mine as he used to be an ob/gyn and so I signed him up. He's been excellent and very informed.
Other things you can try include giving up sugar (man, it's hard but it works), using evening primrose oil to help regulate your cycles, and Angus castus - I never used AC but I did have some success with EPO. Low gi dieting is great if you don't have a sweet tooth and like meat, eggs and cheese :) I used to say to myself : do I want that bar of chocolate or a baby? I had it written on my fridge! Dh dieted with me too: the weekend we gave up sugar was awful, it makes you cranky for a few days so we just shut ourselves in the house and slept! But it makes a huge difference if he's on board. He basically ate what he wanted during the day and did the diet when he was with me - this was for the best as otherwise he would have lost the weight at a faster speed than me and I'd have been all 
Pcos is horrible but can be managed. I do sympathise. Sorry I seem to have written an essay but I've been battling this condition for over a decade and have started to win. It can be done, but you need help and support, starting with a good gp who knows what they are doing, a good gyn consultant, and support from your dh. You can do it, and you will be so happy with your baby in your arms at the end of it all. :)