After going through your complain i suggest you to be calm and don't panic.
As your query regarding
pregnancy it is possible when semen drop into vaginal cavity.
It dosn't matter whether penis inserted half or full.
Some of following Faqs being pregnant during intercourse are following:
1-If intercourse done within period chances of pregnancy increases.(Fertile period means 11th DAY TO 20th DAY of Menstrual period cycle.)
2-Whether a single drop of Semen inserted into vaginal cavity during fertile period chances of pregnancy increases.
3-If you done sexual act during these days possibilty.
4-Another fact for delayed period is some kind of
stress it is also cause delayed period.
5-I will suggest you to go for urine test which can be done easily in home by pregnancy test kit available in medical store.
6-Go for Gyanecologist for better and safe advice.
Hope this help you query.
Hope for better health of yours.