I got pregnant with my daughter when my son was six months. They are 14 months apart and are each other's best friends. My son is almost six and my daughter is almost five and they are joined at the hip, except while in school.
Now the big question is if you are breastfeeding or bottle feeding. I was bottle feeding when I got pregnant, but my friend who also got pregnant when her baby was six months, was not able to continue nursing her daughter because her milk supply dropped around the time her daughter was eight months.
It is a huge challenge to be pregnant and have such a young baby, and it will be a challenge when they are young. But, looking back, I think it was awesome and I am glad they are so close in age.
You need to take care of yourself. Rest when you are tired, eat well...all the normal advice, but having young baby makes it more of a challenge.
You don't mention your social situation, if you are married or not, if you work or not. If you are married, you need to make sure your husband helps in every way he can, even getting up at night so you can rest sometimes.
Good luck to you.