I feel so lonely inside it physically hurts me everyday, what do I do?

I feel so lonely at 30 yrs old and no prospects in dating or serious relationships. I work full time and go to school full time, I have no pets and even if I did I wanted companionship but I dont think a pet would do it. I have some close friends but I tend to keep a small circle and most of my friends are now married or have kids and are too busy with their own lives.

I have felt so lonely that it physically hurts me. My thoughts are so depressing and fill the silence on my car drives home. I feel my tears swelling up as I write this and it's hard to type but I dont know how to make it stop. Some days are better than others but today has been extremely rough reflecting on certain things. I feel kinda lost about how I feel other than I am all alone, that I know for a fact. So I wonder if anyone else feels like I do? It hurts my chest and I can't sleep and when I wake up I'm tired and have no energy at work and ti affects my mood. I feel so much on the outside of what everyone I see is enjoying. I feel like my time has passed or I have been overlooked and I dont know what to do so I just struggling through it. The pain hurts so much sometimes I feel like I'm really pathetic for feeling this way but I cant stop it and dont know how. Involving myself in the community and activities requires more time and extra money I dont have right now. So far the only thing helping me cope day by day is my mountain of work I have with school. But in my free time I feel like Im emotionally and physically in pain.

What do I do? Do you feel this way too?