I have a very hard time starting my bike and now it won't stay running unless I keep on the throttle. I just changed the oil and the oil filter and now it is doing that. I have felt this problem creeping up in the last week or so by the way the bike runs. Even when I get it running and then come to a stop it cuts right off and I have a heck of a time starting it unless I hot start it and keep it throttled up. My idle adjustment is all the way up. Even before this it was all the way up and still barely staying on when idling. I'm not sure what the problem is. Can someone please help me?  

many possibilities, ut the first that come to mind are:

check the air filter to see if it has oil in it.

the fuel/air mixture could be off.

the rubber intake boot could have cracks in  it.

the carburetor has dirt or water in it or both.

my first check would be the air filter, then i would visually inspect the intake boot for cracks.
if not then remove the bowl from the carburetor and look inside to see if there is trash or water inside.

if not i would then while the air filter cover is off try to crank it, if it gets better, then the fuel mixture is too rich.

if it gets worse or stays the same the fuel mixture could be too lean.