Need some help plz! harvest time and ive found seeds!!

hi guys just come to the end of my first grow and ive bin chopping away at my main plant today to discover what looked like unopened buds, when i pressed them a seed came out! looking over the plant i found about 20+, but my plant has produced bud aswell! help is my plant a mixed sex?? should these be there, because i dont think they should?? will this effect my plant as i have took them off?? and could i use these seeds or will this equal them plants becoming mixed sex?? and last thing, how does this happen or was it my cuttins, where they already mixed sex?? thanks plz post some answers so i can learn from this. thanks guys