Earlier Today I Started Getting Light Pink Discharge When I'd

Earlier today I started getting light pink discharge when I'd wipe. Then it got heavier and turned red so I figured I just started my period and put a tampon in. Then when I went to change my tampon there was hardly any blood on it and it had been 3 hours. Normally I bleed heavily red on my first two days. After that I just started spotting light pink again.. I'm cramping like I'm on my period. My breasts are sore like normal. But why am I just spotting light pink?