implantation cramps..

I was wondering if anyone else ever experienced super bad cramps? I'm wondering if it was implantation cramps. Yesterday morning I woke up got dressed went and ate lunch with my husband came home and I was in so Much pain I had to kneel over just to walk it felt like someone was stabbing me  I'm not due for Af for 4 more days. I took a nap at 2 and woke up at 5 and it was all better. I was literally crying it hurt that bad. but not nearly as bad as I did earlier in the day. Today I feel 100% better. We've been ttc for a while now and I just am wondering I took a pregnancy test way early and it said negative. I can take one tomorrow but was wondering if this has ever happened to anyone else ?