Car swaying which get worse if the conditions are windy

I have a Honda Accord, 1993 Sedan with Mileage 148000.
Lately I find that the car sways a little bit on highways specially when the conditions are little windy. I had got the alignment done about 8 months back and have new tires and I was having a very smooth ride. I have checked tire pressure and that does not seem to help. On quiter days, I do not have problems but gets amplified when it gets windy.
Dont know what and where the problem is.