Constant memory loss. At this age?

From the past 1-2 years, I'm able to notice that my memory and reasoning power is depleting. Sometimes, I forget things which I have seen or learnt just 5-10 min back. Nowadays I find so much difficulty to remember things. I was very good at Maths, the problem which I used to solve easily earlier, nowadays I find it difficult to solve the same. I could have remembered many things earlier, but now I cannot. I keep forgetting. Sometimes I cannot remember frequently used things(Ex- my email id which I use it everyday)Why is this happening to me at this young age. I have never taken drugs nor I was into smoking. In the beginning I thought this is common. But now,this is worrying me alot. What shall I do? Why is this happening at this age? Please help me...