I wasn't even out of hospital before I was getting asked when the next one is! And it didn't stop until about a month before I fell PG with DD. If you aren't sure then the best bet is to wait a bit, even if its only a couple of months. Your DD is still young and is at a demanding age. As far as coping with 2, I was so scared I wouldn't be able to handle 2 because DS is very demanding at times and throws tantrums etc (not all the time) but its really not as hard as I expected.....some days are but kids can't be perfect all the time I guess
Can you and your DP come to a comprimise? Do you still want a 2nd baby but with a larger gap or your not sure if you want a 2nd at all? There are pros and cons with close age gaps and large gaps, so really its between you and your DP and when your ready. I'd be telling everyone else that your not having anymore, it might get them off you back (hopefully anyway!). Good luck, I hope you can work it out