My boyfriend's mom hates me and i don't know why? :(?

i'm 18 and he's 19, we been together for almost 2 years now, but his mom absolutely HATES it when I go to her house and visit my bf!! When I see her anywhere I say "Hello ma'am its nice to see you today" I smile at her and ask her how she's doing, all she does is give me a VERY mean look and says "oh hi" Then just yesterday I went to his house in the afternoon, I rang the doorbell and as I waited for my bf or one of his family members to open the door his mom came from the store. She went up to the front door, acted as if I was not there swung the door open very hard! then just walked into her house without even saying hi after I smiled and said hi..I talked to my bf, he talked to his mom but all she said is she does not care how I feel and just doesn't like me visiting, my bf tells me to just ignore her, and that although i'm not welcome by her, i'm always welcome by him...I know that's sweet of him...but I really don't wanna be there knowing his own mother hates me..:( what should I do? i did NOTHING wrong to him or his family,i'm polite, and when i travel with my family I bring them gifts and such, i'm a full time college student who does not smoke or drink, i have been 100% faithful and respectful to my bf...can anyone tell me if there's a way to fix this? thank you