Is it normal to feel this way after a breakup?

I've been broken up with my ex for about 3 weeks. While in retrospect it wasn't a relationship that was meant to last for the long haul, I've been feeling rather introverted since we broke up. It was my first serious long-term relationship. I've had trouble finding the desire to socialize since we broke up. I tried to get out and socialize today, and it just wasn't fun.

I'm 27, and I'm trying to finally get my life together at this point in my life, including finishing grad school and starting my career, and I've had to push myself through every obstacle with little emotional support from my family. It's been hard to meet people with finances being a constant worry without a career to keep me afloat. I did feel that my ex was the answer to a lot of my problems (companionship, support, someone to do things with) over the past year, however, he had no clear long term goals for himself and did not want marriage or children. To make a long story short, we were both in a similar place in life when we met a year ago; however, I was trying to move forward, and he seemed content to stay where he was.

I'm normally a very extroverted and social person, however right now i just want to hide from everyone. Wondering if this is normal following a breakup. I've texted a few old friends of mine who I lost touch with over the course of the relationship, and haven't heard back. Basically, I'm lonely but part of me is enjoying it and not wanting to put myself out there. Wondering if these feelings are normal?