Carry on doing what you are doing lovely! This is a hard time of year for everyone (January blues, cold weather, dark nights) and for you you have the added stress of exams - but that is only short term.
Your university saw potential in you as an excellent student to offer you a place. Your daughter will be so proud of you when you have a career and show your child what a strong, independent woman can do.
I am a single parent to a toddler and I am doing the PGCE year so I know how you feel. There are times when it feels overwhelming, but then I wake up to a new day when things seem absolutely fine. Ups and downs - we all have them.
Don't be put off by negative comments regarding teaching and the long hours. I feel that primary school teachers seem to have a much higher workload possibly than secondary school. It seems, like me, you will be doing secondary with science which from my experience is completely manageable. If you are organised you have free periods to prepare for lessons and it is such an enjoyable vocation/career and extra work can be done once daughter goes to bed.
Think forward to when your daughter is at school and you are a teacher: what other job can give you the holidays so that you will have lovely, quality time with your daughter? That is a huge weight off your shoulders knowing you don't have to worry about childcare for half terms, easter, summer holidays etc.
You may not be spending much time with your daughter now (which is tough I know, maybe put the study books away for a few more hours if possible?) but your choices now are very likely to mean that you will spend much more time with her when she is growing up. Time that she will remember and cherish.
Do whatever feels right for you, and your daughter.
I wish you luck and be proud of what you have got: a beautiful daughter and an excellent ambition and work ethic :-)