Well, it honestly might have been hormones that changed the curl pattern. However, if you make improvements with your hair's health, you might get some curls back!
1. Cut out sulfates! This is anything like sodium lauryl or laureth sulfate, amonium lauryl or laureth sulfate, etc. These are ingredients in shampoos that are not good for your hair. Look for a gentle, sulfate-free shampoo. Shea Moisture Moisture Retention Shampoo has really good reviews
My cousin is a swimmer, and it works well for her.
2. Cut out silicones! These are anything that end in -xane, -cone, and -conol. There are more, but I can't think of them on the top of my head, though...
Anyway, they will coat your hair and eventually not let moisture get in. They can also be pretty damaging sometimes. GVP Conditioning Balm (from Sally's) and Renpure Organics are highly rated.
3. If you want to, you can co-wash, or wash your hair with conditioner. Suave Naturals Conditioners are supposed to work really well for that! You could co-was your hair in between shampoos.
4. Try not the brush or use heat on your hair to avoid damage.
These might make your curls return a little
If not, your hair will still be healthier, and you will still have beautiful 2a/2b waves!