I take the pill 10 days after sex but it's...

have you prevented pregnancy in your case ?
taking those medication in this order wont prevent pregnancy 100% , but the period delaying may be cause by using OCP in wrong way 
What is the options of pregnancy tests ?
1. HCG hormone level blood test
2. home pregnancy test ( urine ) 
3. ultrasound test ( in clinic ) 
How early can you do those tests :
1. HCG hormone test : 25th day of the current period
2. home pregnancy test : first week of the next period 
3. ultrasound test : second week of the next period 
How to know ovulation days and the safe days in period :
1. ovulation time or the time ovum exist are the first 4 days of the last 16 days of the period , for example ;if your period is 28 days , and  if your first day of period was 1st/9 , your ovulation time is 12th-16th /9 
2. the ovum last 48 hours in the uterus and can get fertilized any time during this period of time 
3. male semen lasts up to 5 days in female uterus and will be able to fertilize during this period of time , but the earlier the better