Feeling Lonely and Misunderstood in My Relationship

I'm feeling Low My partners Mother is really getting to me by constantly texting my Partner and making up stuff about me, then telling my partner not to say anything to me. me and my partner sit in the different rooms of the house and I'm constantly feeling lonely I have spoke to my partner but I get nowhere. Like she is bitching about money so my last £30 I spent on buying us dinner then she bitched about no money for the Gas/Electricity. every time I get paid I buy food for the house and pay my bills and give the oldest child money for college and pay the youngest school education. I don't work and waiting on PIP assessment due to having tumours in my knee. Am I just being dumb and over thinking this?