I've spent lots of time in bed while tapering off ativan (lorazepam) + lortab for 3 weeks. Getting up at least to shower/chores/etc then back to bed. Dvt risk?

Being sedentary .... Is a risk for dvt. Bedridden is bad, but people have gotten DVT just sitting for several hours on an airplane. More movement is better, both arms and legs, to lower the risk. Of course, if your condition prevents or greatly limits mobility, prophylactic treatment to prevent DVT may be appropriate. Please discuss your concerns with your doctor.
Cumulative risk. Dr. Accurso's answer is superb. He covers the bases very well. The only thing i would add to what he said is that DVT risk is cumulative so that being in bed might not be the only risk factor involved here. Are you on any other meds besides Ativan (lorazepam) and lortab, do you smoke, are you overweight, have you had a DVT before, is therre a history of DVT in your family, have you had past miscarriages?