haven't jogged with the buggy, haven't jogged at all since I found out I was pregnant

but Oliver should be fine. If his head bumps around a little you could always use a head support like the ones that fit into the carseats. And don't forget to 'fix' teh front wheel when yuo are jogging with it, if it is on swivel you can lose control of it if you go over a bump at speed.
I'm getting back into the walking big time when I get back to NZ, then maybe back into the jogging in a couple of months (once my bouncy boobs aren't so sore!)