Market Force pays you roughly every 30 days, usually between the 10th and 15th of the month, if you elect to have it directly deposited into your bank account. They will send paper checks (that are sent out later than direct deposit) but they prefer you use direct deposit.
When you say you keep getting paid, what do you mean? How is it paid to you? Does it show a ledger from whom it was from? Can you be a little more specific, making sure you are not being sent fake checks here.
And as for sending you the fee and sending you the reimbursement (separately) , the ONLY time this is done is in the state of Nevada. Market Force pays your reimbursements via your bank account and the Mystery Shopping Company you are employed by in Nevada, sends you your fees via direct deposit. (Not all mystery shopping companies in Nevada pay you this way but Market Force does) The fees are different in Nevada. A shopper may make $6 for his/her fee but in Nevada, your fee is usually $12 or higher because your income is taxed as an employee.
Please elaborate further about your pay checks you are receiving....