Ever since I hit 30 (just over a year ago), I've been feeling like time is catching up with me. Most of the people I went to school with have families of their own, while I'm not even seeing anyone at the moment. A lot of them have careers, while I'm still looking for something that engages me enough to stick with for more than 6 months.
None of this is necessarily bad. The fact that you're searching for a job that interests you is a good thing instead of just starting one and sticking with it forever even if you hate it. A lot of people do that. Ditto with getting married.