Hospital Trip and Concerns

Apparently, it is possible to over work yourself when you're basically taking it as easy as you can. Went to the hospital yesterday due to cramping again. Just like when I was 11 weeks. It was caused by dehydration and over-working/stress. The dehydration, I can understand. The stress? I can understand that, too. Especially, with my boss... But, the over-working? I started taking it easy after the first hospital trip. Then, even easier after the Florida trip. 21 weeks, and still having issues that the Doctors consider a "Threatened Miscarriage".... I thought you couldn't have a miscarriage after 20 weeks? Thankfully, though, everything should be okay. Providing I follow doctors orders and take it easy. As long as, I keep feeling Amelia kick and move, I know things will be okay. Even though, when I have any little problem, due to this being a first pregnancy and not paying attention in Health or Sex Ed, I instantly think the worst. No, I haven't done as much research as I should have. It's more like, I hit the 21 week mark, and I look up what to expect that week. I don't look ahead. I'm not sure why, but I guess I just want to be surprised or something.
Now, the concerns part... I'm worried I'm not going to be a good mother. I know every new parent goes through those thoughts, but it really concerns me. Yes, I have my parents, but Amelia will only have one parent. I'm sure I could change that but, (1) her biological father WILL NOT be near her as long as I'm alive and (2) as of now, I'm nowhere close to being relationship material. Which concerns me also. I know some people with Autism/Asperger's can handle relationships and getting married, but I don't see it happening with me. My mom tells me that its because I haven't met the right person yet, but part of me doesn't think there is a right person for me. I'm best when I'm alone. Of course, that won't count with Amelia. I know she's the best thing to ever happen to me. She will make me be a person, she'll make me more responsible, and she'll help me with wanting to be alone. Guess, I should just remember that she is the best thing that will happen to me and that she is the MOST important thing in my life and I should care for her before myself.