Dear Hadi,
Dear Reader,
Thank you for your question.
We don't know the specifics of your situation - for example, how old you two are, what you mean by being "in a relationship," why your parents don't support your wanting to get married now, etc.
Given that we don't know these specifics, we can only give you some general thoughts.
We think, and Allah SWT knows best, that if your relationship does not involve anything haram, we don't see any reason why your Ramadan would not be accepted. Even if you are struggling with this issue, keep in mind that Ramadan is not invalidated by struggle. Allah describes fasting itself as a process meant to build taqwa, not a prerequisite of already having it: “O you who believe, fasting has been prescribed for you as it was prescribed for those before you, so that you may attain taqwa.” (Qur’an 2:183)
If you and this person are getting to know each other for the purposes of marriage and are doing so in an acceptable way, we think this is a good thing that insha'Allah could further your faith. We encourage you to use this Ramadan as an opportunity to ask God to help facilitate this relationship if it is something good for you and to keep it away from you if it is not.
All that being said, we would stress that if your relationship involves something haram, or if you are hiding it from your parents, then this Ramadan is the time to try to change that. Give up any haram parts, remembering that the Prophet pbuh is reported to have said: “Whoever gives something up for the sake of Allah, Allah will replace it with something better.” Perhaps you will be given a relationship with the person you love, or perhaps another person who is better for you.
We suggest that you have an honest discussion with your parents. Parents usually want their children to be happy, successful, and fulfilled in their lives. Why do they not want you to get married? Is there anything you can do to change their mind? As you discuss these questions and try to convince them of your point of view, also listen with an open mind to their point of view. Hopefully, you can reach a conclusion pleasing to all of you.
In peace.