It must be really hard for you, we're ttc and although we've tried not to put pressure on by tracking dates etc. (we're not in any rush and have said we'll just not use anything and see how it goes) but I'm secretly quite disappointed each time it gets to the end of the month and you-know-what happens, which has been 4 times since I stopped taking the pill. I don't understand it myself (I'd just assumed you need 2 ingredients to make a baby and it was as simple as that!) but it seems quite common for people to over-think it and put too much pressure on themselves and it just doesn't happen, then as soon as they stop trying or something else comes along to take their mind off ttc, it happens. It's like your body won't prepare itself properly if you're too wound up and it's a downward spiral.
You don't say why you've put this time limit on having a baby? Is it the urge to have another baby, or is there a practical reason too?
It may also be that something has changed since you had your daughter which is preventing you from concieving, so it may be worth a visit to your doctor to have some tests done to establish if it is a physical problem, or just the mental barrier? If it is physical, it's unlikely there's much they could do within the next couple of months, but there are a few different hormone treatments they can try to increase fertility and if you went down that route straight away, it may mess with your wedding plans somewhat (although it looks like you're giving yourself a year after the baby so I'd be tempted to let this slide a little

)!
There's also IVF which is the last resort if the hormone treatments haven't worked. My cousin and his wife had the treatment after 2 years of trying and got a beautiful little girl. They had to cancel their wedding though, as his wife was almost 35 and I believe (though I may be wrong) that this is the cut-off age for IVF treatment on the NHS.
If you've got plenty of time (and the doctors can't find any reason why you're struggling), I'd suggest waiting until after the wedding to try for a baby when there is no more stress or pressure to put yourselves under. You can enjoy planning the wedding of your dreams and look forward to the fun part afterwards