Anxiety and relationship issues ?

Here is some of my background information that might help a little:

I am an open minded 20 year old Bisexual Female.
I am currently engaged to my 21 year old fiance Krystle, who specializes in auto mechanic.
I grew up in the town of Port Charlotte FL where its large enough to not know everyone, yet small enough to run into people you know every day.
All my life I have been battling mental disorders. When I was a young teenager I was diagnosed with Manic-Depressive BiPolar Disorder, though, I feel as though this was a misdiagnosis.
I have low blood sugar.
I have OCD/feelings of everything having to be neat, organized, and where I like them to be. Im a bit of a perfectionist.
I recently discovered that my 24 year old sister has Narcissistic Personality Disorder. When we were younger, I was molested by her. All my childhood my sister told me how I was too worthless to play with her & her friends. Then she stole my friends so I had none at all. I never really surrounded myself with large groups of friends growing up & being in school. I usually had just a few best friends.
My father was very abusive to my mother and my parents divorced when I was around 8, but it was long needed. My dad has been to a therapist once a very long time ago but when they told him they wanted him to come back because they thought something was wrong with him and they wanted to start treatment, he never went again.
When I was 4 I was in a car crash and suffered from whiplash from then on. I used to suffer from terrible migraines on a daily basis which would sometimes be so bad that I would throw up, but do not anymore.


I currently suffer from low self esteem and anxiety. My low self esteem is affecting my relationship with my fiance. Its an endless cycle that I cant break myself from where I feel like she doesnt love me, that I am not worthy of loving, that I am ugly, etc. Then after awhile we forgive eachother, I explain that I need constant reassurance, we are happy-go-lucky again. Then as time passes it starts all over again and ends the same. Still, neither I nor she understands what is happening.
As for my anxiety, even going to a drive through is tough for me. For those few moments at the pull-up window my mind is frantic. Thoughts race through my head like 'dont forget to check the bag to make sure everything is there' and 'hurry up so you dont make the people behind you wait'. Sometimes I will be so busy with these thoughts that I will forget to get my Debit Card back!! And most of the time I fear going out alone.. even to Walmart. This also affects my relationship because I get very frustrated, aggravated, and edgy.
Also, when things go wrong in my relationship I have kind of this "I KNEW IT!" feeling. Like if my fiance doesnt always kiss me when she comes home, during the fight I will remember that and think "I knew she didnt love me". Not sure if this is some kind of self destruction and I am validating my own feelings. My mother fears that if I do not seek help soon I will self destruct all my life.

One more thing.. I smoke cannabis and have smoked it for most of my life. Although, I do not think it has ever affected me (other than a high).

I know that not a lot of people care about the being of others and I am at my wits end so a big THANK YOU to everyone who is taking the time out of their lives to read this. I really really appreciate it.