I am pretty sure you would be fine with the blankets etc - as long as you dont wake up boiling hot (in which case I guess you would kick off a blanket or 2)??
Re the flu I know lots of ppl who have had it in preg and been ok, I am pretty sure you dont have to worry but maybe check with your GP or someone else on here may know more about it than I do.. I have been lucky and avoided any nasties during preg so not looked into it too deeply.
If your 13 wk scan was good I would tend not to worry myself about it, there are too many things to worry about in preg!
Hope you have a healthy rest of your pregnancy and welcome to the 2nd trimester!