I´ve noticed that when using boyunca a noun comes before like in

Öğrenciliğim boyunca 

hamelelik boyunca  

Is it possible to use a verb like 

Gittiğim boyunca or is there sth else or may be I´m missing something. 

Teşekkürler. 

Öğrenciliğim boyunca during my studies

hamilelik boyunca during pregnancy

Gittiğim boyunca I think it is not possible. As far as I could understand you are asking about construction which means during, while or in period of something. So you can say

Giderken - while going

Ben okula giderken onu gördüm. I saw him/ her while I was going to school.

Agree with Lana. It´s not possible to say gittiğim boyunca.

Boyunca implies throughout a period of time. Gittiğim is "my going" so it relates to just one instance in time.

Gittiğimden beri would be OK if you meant from the time I went up until now.

"gittiğim süre boyunca"

Herkese teşekkürler. 

Then we can use boyunca with the verb if we add süre Ike you said. 

"gittiğim süre boyunca"?

Then is there any difference between the suffix -iken and boyunca?

As you see -ken comes after verbs and it means when. But boyunca is a particle and it comes after a noun. Boyunca means during, along.