Guilt is one of those emotions that are difficult to deal with. It's perfectly natural to feel sad and upset when you leave your baby to return to work. Every family's situation is different and the question of whether to stay home or work only be answered by the parent. There's never a right or wrong answer.
If you constantly doubt yourself and it is negatively affecting your home and professional life, it would make sense to re-evaluate your decision. Take into consideration why you're returning to work, and whether there are other options that could make the situation more bearable for you.
Try to put the time and energy you spend on feeling guilty, towards thinking of creative ways to spend time with baby. Perhaps you could schedule in time every day, for you and baby to enjoy together, even if it's only a few minutes. Remember, parenting is about the quality of time that you spend together, not the quantity.
Working and being a mum essentially means you have two full time jobs. So it is important that you schedule in time for nurturing yourself too. Allow yourself some transition time. Feelings of guilt and sadness around returning to work will lessen as you settle into your daily routine.