On 2nd round of clomid (clomiphene) 100 mg( 3-7) along with injection merional for 5 days ( cd 8-12). why this injection for 5 days?what are the chances of success

Depends: It depends on the causes of your infertility. However, I have concern about your Clomid (clomiphene) dose. It is too high, and it will have detrimental effect on your endometrium. I am afraid that you may ovulate well, but embryo may not able to implant due to thin lining. In terms of5 days injection, it is ok , but i don't think it will change the outcome that much.