All of your , "# weeks" bits are in the wrong spot and your IF() statements aren’t nested.
The , "# weeks" things should be outside your AND() statements and all but the last one should have a comma after them to begin nesting your IF()s. Move every singe IF()'s end parenthesis to the end of the whole formula.
A nested IF() looks like this:
[first thing to test],
"value if first test is true",
[second thing to test],
"value if second test is true",
"value if both test 1 and test 2 are false"