Simple question but as I'm new to dnd I still need some clarification on some things; Say I'm hidden in the first turn of combat and it gets to my turn, do I have to roll a stealth check after every one of my attacks IF I'm using a sniper rifle. 

How I figured this works is before a fight I hide, roll a stealth check to see how well hidden I am, and will not get found unless I specifically run out of my hiding spot or someone gets a higher perception check than my stealth check, but then I wondered; "If I'm using a sniper rifle, that makes a lot of noise, no? The enemies would probably hear the shot and go to investigate the area, but they still might not find exactly where I am, but then wouldn't I have to roll another stealth check because it somewhat revealed my general location to the enemies, or would I just stick with the initial stealth check?"

Yes after you attack you're no longer hidden and hiding again would require the Hide action.

Ok last thing, if I have multiple attacks in one turn do I remain hidden until I fire the last shot or is my position given up as soon as the first attack occurs 

Youère not longer hidden after you make 1 attack.

Here's an official ruling from Sage Advice Compendium on the subject;

If I’m invisible and I become visible when I shoot an arrow at a target, does hiding again require an action? Without a special ability, hiding in combat requires the Hide action

Ok thank you.

You're welcome! Don't hesitate to ask if you have more D&D questions 

Just to add to the above answer -- suppose you didn't actually attack anyone but decided to shoot your noisy sniper rifle into the air just for fun.  You are now no longer hidden for a different reason:

you give away your position if you make noise, such as shouting a warning or knocking over a vase.