I had dc1 at 22.
There are lots of advantages of having DCs at this age (as well as the disadvantages).
It sounds like it's been a big shock to you so give yourself some time to get your head around it before you tell DP and your parents.
First go through the practicalities.
If you are considering top then you need to know your dates so you know your timescales for making a decision & for different procedures (eg medical or surgical top).
If you are considering keeping the baby then start taking folic acid and vitamin d (or one of the pregnancy brands) today.
Arm yourself with facts about what will happen. Eg you say you've just started a job. To get statutory maternity pay you need to have started just before you got pregnant, so check this. Check how much child & working tax credits you would be entitled to both on your own and as a couple. (Do you know dp's earnings?)
Think about whether you'd go back to work after the 39 weeks of maternity pay or become a sahm. If wohm then look up local childcare & costs. (& recalculate tax credits)
Think about where you'd live. Are you & DP at the moving in stage? From personal experience I'd advise not to move in before you are ready 'just' because you are having a baby.
How would your parents feel about you having a baby under their roof? Could you live alone in a council or private let? Where does DP live?
Be very very careful about your rights if you move into dp's place. If you aren't working and aren't married he could kick you out at any time with no notice. Don't get yourself into that situation.
How do you feel about DP in the long term? Having a DC is a big commitment even if you dont stay together. You may have to always live near him and have contact with him if he wants to stay involved if you break up. In the long term this could mean complicated blended/step family arrangements.
Lastly how do you feel about babies/children? Do you have experience with them? Did you imagine having them some day?
There's a lot for you to think through, good luck!