Everyone has to do what they feel is right and you definitely should not feel pressured into marrying or having kids. I got married the month after I graduated from college (age 22). I had my first child at 25 and my second at 28. We loved our 3 years together alone, but NOTHING compares to our time with our children. We still go out on dates and are best friends!
That is the timetable that worked for us. On the other hand, my brother and his wife decided to wait until they were in their 30s and ended up going through fertility treatment (didn't work) and don't have kids. My sister-in-law found out in her early 30s that she had endometriosis and wouldn't be able to have children. They adopted and are very happy.
You need to live your own life and be happy with the decisions and choices you make. You certainly don't need to have your life planned out at 21!!
