I think i was abused, but i have no memories of it.. Please help

For a while now I've been suspecting that i was abused when i was younger. I'll try to explain the reasons why i think this..
Well for starters, i remember having some sexual dreams when i was younger. In one, there was a naked man and woman and they were touching each other a bit aggressively and kissing each other. I also remember enjoying the dream, and i wanted to have it again.. yikes.
And one time in kindergarten i was playing with 2 toy horses with my friend. I started making kissing noises and pushing the horses mouths together and putting one horse on top of the other.. my friend asked what the horses were doing and i told her they were having sex. Then, she asked what that was, so i told her. I don't remember exactly what i told her or if it was accurate, but i told her something.
And as weird as this is to admit, one time i was in my room playing with my Littlest Pet Shop toys, and i got up, locked the door, undressed myself completely and started rubbing them on my downstairs-area. I also remember pretending my imaginary friend (who i had named Tucker) was doing it.. And when my mom knocked on the door to ask what i was doing i told her i was trying to take a nap. I think i was between 5-8 when this happened.
How would a child know what sex is? What caused those dreams? And why the heck would i put things down under?
And as for now, (i'm not sure if this has anything to do with it but i'm assuming it's worth the tell)school has always been an issue. Ever since elementary school I've hadm many, many absences throughout the school year. It's not that i didn't know what i was learning or that i was being bullied, (my teachers have told me that regardless of how many school days i miss i always seem to catch up very quickly. Often times i can miss up to a whole week in a row and only need a day or two of catching up) I've just never liked going. In middle school it was somewhat because i didn't feel like i fit in, and i felt like one of the "weird kids". But yeah. And i know that's an issue, but it's not one of the issues i would like to discuss at the moment.
One more thing. I had severe behavioral problems until i was about 12. I would throw HUGE tantrums, scream, and cry. It was terrible! I would get so freaked out and i'd start screaming and yelling and crying, and occasionally if i got really frustrated i'd start hitting my legs really hard with my fists. I also had insomnia, (still do) and i would stay awake in my bed for hours not being able to sleep. Anyway back to the tantrums.. they were bad. Sometimes i threw one every day for a whole week in a row, sometimes i went a whole week without one, but they were in general pretty often. But when i was 12, i stopped. (yes, they lasted til i was TWELVE) i don't know how i stoppeed, but i did. It went from non-stop tantrums to none at all. It was crazy, but i'm thankful.
Anyway, i need advice. I have those weird memories, and behavioral/ psychological issues ( i have ADHD, bipolar disorder, insomnia, & had Depression ) so could that mean i was sexually abused as a child? I have no memories of actual abuse, but that could mean they are just repressed. Also, if it helps, i am a 15 year old female.
Any help is appreciated! Please & thank you.