At three weeks after liposuction, a tight fitting garment may not be necessary. I often recommend that my patients just use the garment for when they feel they need extra support or for those instances when it seems to provide some comfort. If it is at all uncomfortable, then I would not wear it. I also recommend a department store type girdle or garment after the first week as these oftern provide plenty of support and are more comfortable than the post-op surgical garment.
Light exercise - such as light walking - may improve healing by increasing circulation. I would not do anything that is uncomfortable so adjust your pace and your activity to your comfort level.
Some patients have relief from very light massage using a hand held massager and light pressure. Avoid excessive heating pad (no more than 30 minutes at a time and only low setting) as this can cause a reddish-brown discoloration to the skin.