You may be experiencing post-partum depression, which sometimes can last for months after the birth of a child. If your baby is just a few months old, you will probably have at least one more examination by your obstetrician. If so, talk to her or him about your feelings. If you have had your last examination, talk to either your family physician or your baby's pediatrician. An appropriate referral for counseling could be made from there if it seems necessary.
And I suggest that you talk to your baby's father: you may be feeling overwhelmed because you don't know what your future (or that of your baby) will be like. Your boyfriend helps you one day a week now, but there are six additional days in every week. Have you definitely established, and has he acknowledged, paternity? This may not seem important now, but down the road it could be critical for your baby's future. Don't put it off.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.