Using devices/piss sticks/temping can drive you a little bit crazy, so I would always recommend at least a couple of months of simply shagging first, TBH. If you do it at least every couple of days from after the end of your period, you should get there, assuming you have "normal" 28-30 day cycles with ovulation in the middle.
My next move would always be temping, because it worked for me to get DD1, and because you can using temping to (in theory) discover you are pregnant without the need to pee on a stick right away. I would swear by fertilityfriend.com
Most people I know who have used the clearblue fertility monitor have done so only after trying for a while without success, partly because it's so expensive and partly because it can drive you a bit mental so be warned
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Thanks for the vitamins reminder, I should really get some. I just took pregnancy vits from TTC onwards last time. No real brand preference, although i seem to remember some people having issues with pregnacare. They didn't bother me though.
As this gets closer, I'm starting to panic about whether I can really cope with two children!