Are you abe to continue playing the game after the main questline without having to re load a previously saved game?

The MQ is not the end of the game. The game doesn't end until you decide you're done no matter what you've completed.

Not only that, you don't have to sit through a long end credits sequence after its over

^^ this as of right now I have 90something quest done. There really isn't an end until you feel that you have done all that toon can do, then you start a new toon

The MQ is only part of the game, and optional at that. Some never finish the MQ, some never start it, some get it out of the way early, some delay it as long as possible.

To specifically answer your question, the game continues after the MQ is over.

To sum up what everyone said in the comments: YES YOU CAN

Well I played 400 hours and I didn't finish the MQ , I have two more hold COMPLETELY not discovered , and well , there's a lot more to do.
Dawnguard for example , I think I will start it in a year.

I did the MQ as fast as i could on my first character. Because i was eager to see what it was all about, then i deleted all save files on him and made 1000000 other toons to do other things with (most non dragon borns but still)

of course you can.
u can finish the main quest first and then do other quests later
the game never ends only when u want it to

as soon as i get out of helgen, i purposely fail the first quest by killing alvor, so i dont do the main quest, then i just go out and explore