2001 Volkswagen Beetle help

Every time I start my car it sounds like a motorcycle, I can hear and feel the engine very loudly, it even idles loudly. It just started happening about a week ago, it had been starting up fine, no loud noises or anything. But now every time I start it, it sounds really loud. I had thought that there was a crack in the muffler but I checked and I couldn't find anything. I've driven it on the freeway a couple times and it gets even louder. It starts to shake if I go to slow in gear and it feels like it's having a hard time when I rev it over 3000rpm
I just had the oil changed about a week before this started happening. I want to take it in but I would like to have an idea of what it might be before just so I don't get ripped off.