The establishment has to release salary slip, salary of the month in which employee has worked for days worked e.g. April as posted by you, on usual/fixed pay day…………….
The employer can very well allow clubbing/adjusting other leaves by IT’s sweet will……………..
You can try for IT..
If employer does not agree then IT may not allow [paid medical leave beyond limit of medical leave and beyond that may approve on LoP/LWP (without discontinuity in service.. and you may confirm IT.)..
Submit leave application in time and under proper acknowledgment and keep all supporting docs e.g; Medical advice/Rx, medical certificate, Lab tests etc..
The c/f leave (earned) that can be encashed can continue to accumulate and can be encashed at the time of separation….