I’m 13dpo and my period is 4 days late... can it take longer to get a positive with a short cycle??

Okay so I’ve been off birth control since October 2018 and me and my boyfriend had unprotected sex and he finished in me on 2nd of January and 6th of January, I ovulated on the 9th.

I have been feeling very odd with cramps now for the last week maybe.. I am also having a lot of sticky thick clear cm along with a really weird bubbling/vibrating feeling in my belly. Also the last 2 days lower back ache. My outside of my nipples also look as if they are changing colour.

So I definitely feel like I am pregnant as I’ve never had any of this before... I don’t even get cramps with AF and she’s never late. I did a first response test yesterday at 12dpo and it was negative.

I do know that I have a short cycle, can it take longer for you to get a positive if your cycles short??? I’m gunna retest when my periods meant to finish on friday🤞🏼

I’m just thinking that something’s GOT to be happening as my period is like 4 days late...