As per the present legal status in India, the children will automatically get the caste of the father. So you will actually be an OBC. But you have opted for your Mother's caste. This has happened without your knowledge. So you can definitely contest and get the correct caste certificate.
Immediately you approach the MRO of your area with the caste certificate of you, your father and the mother. You tell him that by mistake you had been given a wrong caste certificate which is not as per the law. Then he may accept your request. Then you can give it in writing to him by attaching the copies of caste certificate. Then he will conduct an enquiry through MDO and VA. Then he will give you the correct caste certificate. In your application, you can mention that by overlook you have missed this point and you have lost many chances you get as OBC.
I know two cases like this in which MRO has issued new caste certificate as per the existing law.
If the MRO is not giving the required certificate, you have to contest the decision of your parents in the court. Then the court will conduct an enquiry and they will arrange for changing the certificate. For this, you have to contact a lawyer who is very well versed in these issues and he will guide you properly to get a positive result.