I disagree with what the other one said about waiting so you can bond. You've already bonded! My first two children are only 14 months apart. I got pregnant with my second child when my first child was 5 months old. We would do it all over again and again and again, if we could plan it that way. But getting older, I suspect, is my problem in not being able to get pregnant when we wanted to.
It is wonderful to have kids close together. What a blessing it has been for us!
As far as being disappointed, I would totally understand that. You get used to the idea that you are indeed pregnant and then it can easily get bashed with having a period. But just because you have a period doesn't mean that you aren't pregnant. I spotted a good bit...conceived at the end of December and then had a regular period in January and still spotted here and there through March. I'm have way through my current pregnancy and all is well. (This is actually the first time, I spotted so much.)
I would go for it if you are feeling great about it. Go for it!