I would go to a new OB as I think you would be better with contiunuity so you can build trust and speak to them if you have any issues etc, if you see current OB and then towards end of preg get there fill in you might not gel and like them and by then too late to change OB's.

No reason why you can't make a few appts with a few obs go and see them and then decide who you want.

Good luck

xoxo