Hi
Yes, it's 12-18 months unless you're over 35 in which case they want to see you within 6 months.
No point telling them you have TTC before. I had and it didn't make any difference, they still wanted me to go 12 months this time round.
That said, when my IVF Consultant found out that OH and I hadn't really used any contraception in the last 4 years (I'd half-heartedly used the cap and other than that we used the rhythm method) she put 4 years infertility down on our record.
I wouldn't go after 4 months, you just need to give yourself more time. I saw my doctor at 8 months and he told me to spend the next 4 months using OPKs and then come back. I also did temping and took all my graphs too which were really helpful. Also keep track of all your AF dates and length of cycles.
Get the Toni Weschler book, chart and use OPKs and it should all work fine.
H
xx