What happens if my husband refuses to give divorce even after years of separation?

Yes, you do not need your husband's consent to file for divorce — mutual consent under Section 13B is only one route. You can file a contested divorce petition under Section 13(1) of the Hindu Marriage Act on any of the fault-based grounds available to either spouse, such as cruelty or desertion, and the court can grant divorce even if your husband opposes it, provided you prove your case.

Given your situation of over 4 years of separation, the most relevant ground is likely Section 13(1A), which allows either party to seek divorce where there has been no resumption of cohabitation for one year or more after a decree of judicial separation or restitution of conjugal rights. If no such decree exists yet, you may first need to establish the separation through the appropriate proceeding, or plead desertion directly under Section 13(1)(ib), which requires showing your husband deserted you for a continuous period of at least 2 years without reasonable cause and without your consent.

Long separation alone, without a specific statutory ground properly pleaded and proved, is not automatically sufficient — "irretrievable breakdown of marriage" is not yet a standalone statutory ground under the Hindu Marriage Act, though the Supreme Court has occasionally granted divorce on this basis using its special constitutional powers under Article 142, which are not available to lower courts. This means your case needs to be built carefully around desertion, cruelty, or another recognised ground, using evidence of the separation period and your husband's conduct.

Given the contested nature of this and the specific ground that fits your facts best, I'd strongly recommend a detailed consultation with a family lawyer who can review your timeline and evidence before you file, since choosing the wrong ground can significantly delay your case.