When you combine simple past tense with past continuous, you are showing something that occurred in past and continued for a while in present .
1) I was sleeping from 9:00 am to 11:00 am.
Combination of simple past with past continuous is used to show one thing happened in the middle of the other.
1) I was cooking and the door bell rang.
I was cooking food from 12:30 to 1:00 pm when the doorbell rang at 12:55 pm.
Words used to combine simple past with past continuous :When, while and as.
So, is not used for combining these sentences.
You can join the sentence like this :
Several years ago, as I was having problems with math,I found a tutor to help me.
Or I found a tutor to help me several years ago when I was having problem with math.
If you use when, while or as in the beginning of a sentence, then you need to put a comma after a phrase for e.g. : When I was talking bath, the telephone rang.
I think this has answered your query.