Don't understand why I am struggling to conceive 2nd baby please help..

With my first child I conceived very quickly after using baby prenatals and preseed.. I've done the exact same thing for a while now and still not getting pregnant 😭😭 I've got 3 days until a flow comes so I start my period on Monday and I got a negative this morning and days before but when I first found out I was pregnant last time i had a clear positive five days before my period was due and this is now happening every month when I test days early it's always negative so I know I'm not pregnant 😭 there isn't anything else I can do I'm so upset 💔

UPDATE : sorry I forgot to add that I have been tracking when I ovulate with clear blue and had sex everyday of my fertile day