Have I Compromised my Muscle Repair?

It is possible for a stich to break 5 weeks after a tummy tuck especially if it is not permanent.  However, at 5 weeks, the body has pretty securely fixed the repair with collagen.   It is not our of the question that a repair could be disrupted but it would be most uncommon.  I can't imagine that sneezing or straining in the bathroom could do this.

Considering you are only 5 weeks post-op surgery, it is normal for you to feel tightness in the abdomen area, you have quite a bit of healing to do and the stitches used should be permanent. If you have doubts or concerns that something may have ben affected, consult with your plastic surgeon as soon as possible. Otherwise, take it easy and do not worry too much. Take care and good luck.

A big part of a routine abdominoplasty is the midline tightening of abdominal muscles. Many surgeons use a woven suture that allows ingrowth of tissue into the suture to maximize the strength of the repair. However, this takes several months and may be compromised by strenuous activity.
Avoid stomach crunches, sit ups, lifting heavy weights. Further, previous abdominal surgery may place you at greater risk for disrupting the muscle sutures.