The rectal bleeding
in the irregular periods
are not related. They are two separate problems. The most likely cause of rectal bleeding is hemorrhoids however it is important to rule out cancer. Some hemorrhoids cannot be seen externally because they are inside, which is why you may not be aware of them except by bleeding. You need to get this evaluated by a doctor.
Onto the irregular periods. If your cycle was irregular before you started Depi then there is no reason that they would be regular now. However if your cycle was always regular without birth control pills or other medicine prior to starting Depo it can take a full year for regular cycles to reestablish.
If it has been more than a year since you had a get depo shot then rhe most common reason for regular menses to become irregular is significant weight gain. Other common reasons are thyroid
abnormalities or an elevated prolactin
level. Those two can be evaluated by laboratory tests. Regular menses will resume when the underlying problem is treated.
Untreated irregular periods can eventually lead to endometrial cancer
especially in overweight
individuals but even in regular weight ones. I suggest that you follow this up.
Thank you for your confidence and I hope these answers are helpful.