implantation?

Hey ladies! So this is mine and my husbands first month ttc our first baby. AF is due the 24th of June. We have done the deed everyday atleast 2 times a day since the 4th and my ovulation tracker says I should have ovulated the 9th but I've been taking opks from the 8th till today and haven't seen an lh surge so I'm thinking i ovulated sooner than the 8th..  the past few days I've had cramping (doesn't feel like period cramps) bad headaches on and off throughout the day and lower back pain. I read online that another girl had this happen to her and she ended up getting a BFP! has anyone else experienced this?  Once again Af isn't due till the 24th. so that's another 12 days from now