Say i have intelligence as one of my major skills, and its on a base level of 95. If i fortify my intelligence to 100+, will i still be able to level up the base value when i next go up a level?

I'm not sure of your question, because Intelligence is an attribute not a skill

But if you can still increase attributes and skills if they are fortified to 100.

However some quest rewards, like the Grey Prince reward, are added as abilities and not fortifications. In that case you cannot level over 100. Your can see abilities on the magic effects page. You can also tell by looking at the stat, fortifications are in green, abilities are normal blue.

So, thats a yes.

Also the reverse, if you are hurt, then you can level it past 100. So when an attribute is at 100, get poisoned, then level up. This is the only way you can get past 100 attribute on Xbox.