My advice is - please do not assume just getting pregnant and having a baby will make you happier, that's an awfully big order to place on your baby. A person who chooses to get pregnant should always be happy with themselves first, and be in a good place emotionally before making such a huge commitment and such a drastic life change. The baby deserves a mother who is in a stable situation and emotionally content before it enters the world, that's just my personal opinion. Never assume a child will take away your problems, children add to life's problems because it is no cake walk.
It sounds to me like you're using a pregnancy to distract yourself from how you feel and you're assuming having a child will make you feel less worthless, but you shouldn't feel worthless anyway, and there's no guarantee a child will fix that problem for you.

You need to really ask yourself why you feel worthless and why you're assuming a child will make you feel differently. What are you trying to get? Unconditional love? That is not the child's job. The child will need to be nurtured, and you can't nurture something if you aren't nurturing yourself first.
So please try to be happy within yourself before you decide to get pregnant to replace the feeling of unworthiness.