Soooo I have been using my trailer loads since buying it a couple of months ago

I had noticed occasional 'thudding' from the trailer into my car if anything other than gentle slowing, so I rang the trailer guy a few days back and he thinks there's something wrong with the 'piston' but can't fit me in for about 3 weeks, he said carry on as usual on small journeys for the time being.
Took a friend to a comp this eve, on the way back my car started smelling, it felt laboured etc.
I am worried that the brakes came on as such and made the car have to work harder...(although if this was the case surely u would have really known it?!?) or my car is broken - which is worse as it will be more expensive to fix
Am gutted though as we had planned for months to go to a specific funride on sun, but no-one else has a 510 sized trailer on the yard
No point to the thread, just moaning