My good friend had two German Shepherds, Sirius & Real Sirius.... :)
His latest Shepherd is Thunderpaws....
Concerning for your drain still being in and producung, I will offer some ideas:
* As you are walking a lot (3 miles daily)- this might keep some of the internal stitching bleeding a little more than others might experience.
* My experience (8 major surgeries over 45 years) suggests the benefit of the exercise outweighs the minor bleeding.
* Don't over-do it.... That is, don't pull any stitches. Don't take aspirin, etc. Some other pain killers thin the blood, too.
* Drink a lot of water and take a vitamin suplement with iron.
* When you are fatigued, your thinking becomes skewed. Don't take yourself too "Siriusly" - and rest.