Ttc 7 months no luck

Mi

Regular periods. BD every day or eveey other day, especially when OPK positive. Blood work done no hormonal problems or anything no pcos. Normal sperm quality.

I spotted just now, preg test negative. AF coming I can feel so I’m out.

Why is this happening? It will be 8 months next month. I know a lot of people ttc for years so 8 months doesn’t sound like a lot- but then why did I use protection every single day of my life before this?