13 weeks! Good job. My highest was 12 weeks.
Here's some tips from Redhotlala from her folki:
I kinda stumbled upon not relaxing the hair super straight a couple of years ago. One time, I accidentally relaxed my hair with a lot of oil and grease in it, and the relaxer didn’t take. I was so pissed because I wasn’t use to all the curl and body (The oil keeps the relaxer from penetrating the hair strand). Eventually, I got use to all the thickness and curls, so I continued to apply a lot of oil and grease to my previously relaxed hair before each relaxer. Over time, the hair got fuller due to this.
Basically, I relax my hair just like the instructions in the relaxer kits.
1) Before relaxing, I lightly detangle the hair with a shower comb (the hair doesn’t have to be super detangled).
2) I create 12 parts, I apply a lot of Vaseline, grease, or oil (im sure that they all work pretty well) to the previously relaxed hair (not directly to the roots). I twist each section into a Bantu knot and secured with butterfly clamps. I also apply a lot of grease to my kitchen area, and around my hair line.
3) I unravel 1 section at a time, and apply relaxer to it. I do the front first and the back last.
4)I lightly smooth the hair, probably for about 1 minute or 2 before I rinse. I leave the relaxer on for about 12-15 minutes in total. Depending on how fast I can get it on.
5) I wash my hair about 6-8 times to ensure that the relaxers out…..Two times is not enough.
6) I condition with a mixture of conditioner and oil, and I sit under the dryer for about 20 minutes before rinsing.
To make a long story short, just apply a lot of grease, oil, or vasline to the previously relaxed hair before relaxing. This will prevent overlapping and overprocessing, and over time the hair will thicken up.