I can't really talk about how the kids interact (one being "gone" and the other still gestating) but on the physical side, my body seems to be handling this pregnancy quite well. There was about four months between me giving birth to Ianto and getting pregnant with Cookie, so less than you've said. My muscles in my belly are a touch sore (all the time!), but that might just be normal pregnancy pains rather than related to the closeness of my pregnancies. I say if you want it, go for it!