Grade Point Average or GPA is [Sum( credit hour X grade point) divided by the sum(credit hour)] for that particular sem only.

For example, I take 3 units with credit hour of 4, 3, and 3, and obtain grade point of 4, 4, and 3.67 respectively.
Then my GPA for that sem is (4X4 + 3X4 + 3X3.67)/(4+3+3).

Different uni may have different grading scale, and different credit hours for different units. So without the values of your unit credit hours and grade point, ppl here cant help you.