Assalamu aleykum,
I cannot reply on the fact of this situation being a sin or not, but I would like you to ponder on several elements.
- Marriage is a very important part of one’s life, it affects your future and your spouse’s,
- intercourse is a basic need of every human being, of both men and women, so being in such a situation where no martial relation with the spouse is not advisable and also detrimental for both parts,
I would like to remind you about the Verse of the Holy Qur’an: …[a woman] must be retained in honour or released in kindness.(2:229)
My recommendations are the following:
- try to find a solution to your problems with your spouse, communication is the key for any kind of relationship
- contact a local scholar and or a respected person for your family, talk about your issues and seek advice and help to resolve your problems and have a blessed marriage
I suggest you to read the following texts that may be of help to change your marriage for the better inshaAllah:
https://www.al-islam.org/marital-life-importance-and-issues
https://www.al-islam.org/islamic-marriage-handbook-syed-athar-husayn-sh-...
https://www.al-islam.org/principles-marriage-family-ethics-ayatullah-ibr...
https://www.al-islam.org/marriage-and-morals-islam-sayyid-muhammad-rizvi
https://www.al-islam.org/from-marriage-to-parenthood-heavenly-path-abbas...
https://www.al-islam.org/introduction-rights-and-duties-women-islam-ayat...
In this page you will also find some duaas recommended for marriage:
http://www.duas.org/matri1.htm
Here below also some very interesting videos about marriage:
https://www.al-islam.org/media/ideal-marriage-islam-sayed-mustafa-al-qaz...
https://www.al-islam.org/media/blessings-marriage-islam-sayed-mustafa-al...
https://www.al-islam.org/media/islamic-married-life-part-1-2
https://www.al-islam.org/media/how-make-our-marriages-more-stable-sayed-...
https://www.al-islam.org/media/husband-and-wife-roles-islam-balancing-fa...
https://www.al-islam.org/media/husband-and-wife-roles-society-vs-reality