OP, we conceived our daughter when I was 34, she was born when I was 35. We ttc but not very hard for a few months, and then the first month we used OPK's, I got pregnant. Even though it only took 4 months - I thought those 4 months were hellish, but they are nothing compared to the monthly sledgehammer that hits me each time my period arrives these days.
Therefore I would like to point out that having a child already is not always a good indication that you will be able to conceive again. Otherwise I'd be surrounded by a little clutch of gorgeous children by now. Sadly I am not.
I am now 38, we've been ttc no 2 for 21 months with no joy. We are both fit and healthy, do not smoke, drink little and are of a healthy weight. We seem to have been struck by secondary infertility and it is more common than you think - I think the stats are 1 in 5 couples will have trouble conceiving a second child. In fact I am sure I heard that statistically, secondary is more common than primary infertility. Of course, 'statistics' can be made to say just about anything you like.
I am now awaiting an HSG, DH has to do a sample and we are starting down the 'medical intervention' route. And I am NOT relishing it.
My advice OP would be that if you are desperate to have another child, I'd get on with it sooner rather than later. You may be one of the the lucky ones who falls at the first month (and lets hope that you are), but if you are not, at least time is on your side to get help. Good luck!