The way to avoid DVT and PE is immediate mobilisation. the majority of my patients do not opt for anti coagulants and you need to run through the pros and cons with your PS.
If you have experienced discomfort then this is a sign that you are doing too much. It is unlikely you will have damaged anything but best to see your PS for reassurance.
This is not unusual following the surgery you describe. Always best to be examined in person but from the photos the seroma does not appear excessive. Best to see your PS.