You need to dig up your total prior year contributions any way you can ... you should have been keeping the contribution records ... did you keep the form 5498 from the custodian every year ?
If you still have any prior returns from that far back, you might look at a Form 8606 to see if there are any entries that can shed some light. If you have a investment advisor holding your funds, he may have the answer. You may also have old 5498 forms.
If you’re sure you're not going to tap your account until retirement—specifically after age 59 and a half—you don’t have to bother to keep track of your contributions. All withdrawals after you’ve reached age 59 and a half and had the account at least five years are tax-free and penalty-free.