4dpo cramps back ache 1st TTC any advice is greatly appreciated

So I know it’s to early for implantation to happen. But today for a couple hours I had like a few sharp pains then turned Into cramps and I had a lower back ache. I never have back aches and I only get the cramps when I’m a day or two away from AF which starts the 23rd. I got a peak clear blue advanced test on the 7th and ovulated on the 8th. Any reason why I would be having back aches and cramps, I’m almost really tired ? Any advice is greatly appreciated