Hey sweetie, its ok and completely understandable that you feel overwhelmed. Parenting is a big job even with a partner, let alone by yourself.
You love your baby, these are only passing negative feelings because your coping mechanisms are low at the moment.
I would suggest the following to help build you up:
Join a mothers group, so you and your baby can spend a small amount of time with other mums and babies each week. There may even be a single parents play group. Look into it, ask your doctor or the local maternity unit, they usually know what's available.
I'd also see your doctor and tell them how you are feeling, they may suggest anti-depressants for a time to help you. Or maybe some high concentrate fish oil.
Look into counselling. Its great to have an objective person to unload on and get advice from (I do this).
Keep your support network of family or friends close and try branching out and making more friends. If you take your baby to the local park you are likely to run into other mothers.
Just remember, you are a great mother and these feelings are expected when you get overwhelmed, just reach out for help.