Can the days I have fasted be counted as making up for the days I missed in Ramadan?

For the validity of a missed fast (qada'), it is a condition to make the intention during the night and to specify that it is a qada' fast. Therefore, whoever fasts without the intention of qada' will not have that fast count for the days they owe.

The intention is obligatory, and specifying it is essential, based on the Prophet's (peace be upon him) saying: “Indeed, actions are by intentions.”

Accordingly, what you fasted without the intention of qada' does not count for you, and you must make up those days with a pre-dawn intention for each day.

If you delayed the qada' while knowing the impermissibility of delaying it beyond the next Ramadan, then along with making up the fasts, you must pay a fidyah (expiation) of feeding one poor person for each day you delayed its qada'. However, if you were ignorant of the impermissibility, then nothing is required of you.