Please speak with your OB GYN doctor
or your primary doctor. It is not completely clear from your question where the bleeding
is coming from, and that is definitely the first thing to sort out. If the bleeding is vaginal (but occurring when you strain to defecate), then this could be irregular menstruation or breakthrough bleeding (common after giving birth) or several other gynecological problems.
On the other hand, if the blood is mixed in with your bowel movements, then it is probably coming from your gastrointestinal tract. By far the most common cause of blood in the bowel movements are hemorrhoids, which again are very common after giving birth and which can be made worse by constipation. On the other hand, there are other more serious causes of gastrointestinal bleeding, such as a stomach ulcer, and these all need to be ruled out.
I'm also uncertain what you mean exactly by a "problem with your septum" after giving birth, although if you mean that you had some trauma because of a vaginal birth, then it is also possible that the bleeding is from a laceration or other wound that has not healed very well.
Regardless of what is the final cause, the first step is for you to get help from your OB GYN doctor, or your primary care doctor
- they will be able to help you figure things out.