Dear sister, your mother-in-law interferes because your husband is giving her the licence to do so. She has the green light!
The problem lies within your husband's behaviour.
There are matters which are of no one's business but of a husband and a wife. There are clear, healthy guidelines which are common sense really, as to what matters pertain to a husband and wife relationship (and therefore are shared only by the two) and what is appropriate to share with one's mother.
Your husband did not marry his mother. There should be no competition between how much attention he gives to you and how much he gives to his mother. Mothers sometimes find it hard to let go of sons. For such mothers, it is a selfish act and an unthinking one. All you can do is be kind and tolerant and perhaps in time, she will grow to accept you and stop looking for faults in you and perhaps look at improving her own shortcomings.
Your husband really needs to help here if things are to improve.
Singlehandedly, you do not stand a chance of changing the dynamics of what is going on. But with the help of your husband, the two of you COULD change things around. You need the help of your husband.Ask Allah Subhanahu Wa Ta'ala to help you with your husband and his mother. Ask sincerely in your duaa. If you could get your husband onboard and if he could in a gradual manner discuss you with his mother less and less, then your other problems would or should resolve themselves. you see this is the chain of events which you have going now:
Your husband complains and tells all to mother (what on earth is he doing telling her, for how can things get better if he does not tell you??)
Mother is given more fuel to say negative things. This keeps her momentum going.
Mother goes around telling family including your husband's brothers and sisters
All the family are hearing negativity about you
Your husband loses your trust in him. (any wonder, after all this!)
You need to talk and explain all to him.
He should cherish you, protect you and hold you in high regards. He should be caring and sensitive to your feelings. You are an important person in his life.
Allah SWT says:
“And among His Signs is this that He created for you wives (spouses) from among yourselves, that you may find repose in them, and He has put between you affection and mercy. Verily, in that are indeed signs for people who reflect.” 21:30
Anything that he does not like regarding you, he should discuss ONLY with you and NO ONE ELSE.
Allah SWT says:
“O you who believe! You are prohibited to inherit women against their will; and you should not treat them with harshness, that you may take away part of the Mahr you have given them, unless they commit open illegal sex; and live with them honourably. If you dislike them, it may be that you dislike a thing and Allah brings through it a great deal of good.” 4:4
This is the common sense of how to run a relationship in a marriage if one cares enough for it. Unless it is an utterly unhappy marriage on both sides, every marriage should be treated with utmost care and wisdom for it is from Allah.
You also need to understand the special place that mothers are given in Islam. You cannot challenge this and one should not want to. She should be respected, obeyed (when it is a righteous request, not one that is evil), assisted, cared for, all of these things.
If mother in laws were more careful and respectful of their son's / daughter's marriages, many more marriages would have survived.
Being harsh with the daughter in-law or son in-law is not supported in Islam:
Abu Hurayrah may Allaah be pleased with him reported:
“I heard Abu Al-Qaasim (i.e., the Prophet) sallallaahu `alayhi wa sallam ( may Allaah exalt his mention ) say: "The miserable one is the only one whose heart is deprived from mercy." [At-Tirmithi]
To sum up, you need to be patient and get your husband to be supportive of you. If both of you sincerely asked Allah SWT to help you and guide you in saving your marriage things could fall into place. Human relationships are never easy and require lots of effort.
May Allah SWT help you in resolving your problems and replace them with love, peace and tranquility.