We're sorry to hear of your miscarriage. We understand that keeping these halachot at this time can be difficult and greatly value your depth of commitment to halachah.
The procedure itself rendered you niddah. Therefore, the day of the procedure is the first day of the five day minimum. Assuming you get a valid hefsek taharah on day five, you can count your seven days starting the day after the hefsek taharah.
You state that the pregnancy ended at 7 weeks and 5 days. We assume that you mean from the last menstrual period. For halachic purposes, the length of pregnancy is calculated from the date of presumed conception, which is generally the date of last mikveh use. Thus, it is possible that your miscarriage occurred less than 40 days after conception. If that is the case, you can immerse immediately upon the completion of the seven days just as you would for any other episode of being niddah. If the miscarriage occurred more than 40 days after mikveh, you cannot immerse, even after completing the clean days, until fourteen days have elapsed from the procedure.
Please write back with any further questions.