Answers

You must have paid without inspecting the work. Building code requires a weather barrier under the siding and that it be taped at openings and all seams. Was there a permit obtained to do the work? If not, did your locality require one. If they did, report the contractor to the inspection department  as having not pulled a permit and gotten the right inspections. They may be able to help you and it oculd be a license violation in your state. Although most will refuse if a permit was not obtained and the proper inspections performed. Maybe they will go after the contractor and have them make it right. Have you checked your ceiling insulation? Heat rises and if the attic is not properly insulated(This is where 2/3 of the heat escapes from a house.  and  the soffits(overhang)need to be  vented. Heat will escape through the roof. How about your windows. Caulking around the j- channels where it meets the frame may stop some air and water infiltration.Do this with a clear caulking made for that purposed.  A lot of heat escapes through windows if they are not properly sealed. You may be able to put some plastic film over the windows and inside casings like 3-M. This may also help you with heat loss. There are foam inserts that you could put in the electrical outlets by removing the cover screw ,,pulling the cover,  putting them in place and then puttng the screw back in. Maybe the walls should have been insulated while you had the siding off. There are many things you havent't told us but these are ideas that may help your situation. It sounds like you do not have a foundation with blocks. But they are also a souce of heat loss. If you do, you could insulate the rim joists with a high density foam sheet and cut them to fit. and then use caulk or spray foam to seal around the edges. Hope this helps you.  

1. to make sure all crawl space vents are close .

2. you can check all exterior doors and windows do not have air leak .

3. check attick insulation should be minimum 10'' or you can add more insulation .

4.  you can cover large exterior window's glass with clear 3mil plastic .

5. you may check your heater system , and air filter need to repace every month .