When I was little I was terrified of water. I know I didn't almost drown when I was little or anything like that. At first I couldn't have baths unless my mom or my sister was with me. I could not wash my hair in the bathtub where my head would go under water. My mom had to do it in the sink until I was six. When we played in kiddie pools or the sprinklers if any water hit my face I would start crying hard.
Now I still get anxiety attacks in the water. I didn't learn how to swim until I was ten and I'm still not a strong swimmer. If my feet get to a point where they aren't touching the ground I start panicking. The last time I went to the beach I got caught in a wave and almost drowned because I was so scared. If my one guy friend hadn't been there to grab me I probably would have. I'm thinking I must have drowned in a previous life, probably the one I just had.

How do you really find this stuff out? Also I am deathly afraid of centipedes and spiders. Not just because they are creepy looking, but just because of what they are. Could something have happened to me with them as well in previous lives?

Sometimes I remember rooms in a mansion. I have never ever been a mansion. I can remember the rooms and the stuff in them though. All the stuff in the room is stuff that people used in the olden days.

Definately sounds past life-ish to me!

Sometimes we carry over the fear and karma from other lives and this can trigger problems like you have described.  The best way to stop the memories and lesson the fear is to revisit them and understand them and then cut the cords that tie that memory to this life.

See if you can recreate the atmosphere and then see the memory, look at it from all sides, try and see why you are frightenend, why it has lingered, what is it you should have learnt from it and then learn that lesson now. Is there a message you have to pass on, or have missed reading? Was there something you could've done but didn't, do you regret something did you miss saying something?

Once you feel happier and you have done this gather the whole memory up and envisage placing the memory pictures firmly into a safekeeping box, this could be a wooden box, a gold vessel with a tight lid like a genie bottle, or even a suitcase, whatever you feel is the best place,  make sure all the bits and pieces and any stray threads, or ropes or cords and all cut and broken and placed into the vessel too so that the whole memory is removed, then watch yourself destroy the case or jar or perhaps bury it or burn it, you could even throw it into the sea depending on how you now feel about it. You may even want to put is safely into a dark room so that you can revisit it again and learn more one day.

Take it slow and see how you get on, remember that you can always leave and come back to the present any time you want.