Hi Megan, there is never a need to feel alone as Our Lady Mary Mother of Jesus and Jesus are right there alongside of you as you are Baptised.
Further to Julianne’s advice, I wish to add the purchase of Rosary Beads then for those to be Blessed by your Local Priest when you attend Reconciliation/Confession. These can be purchased at the Catholic Bookshop or Christian Bookshop in your region; thereafter commence opening up your Heart to Our Lady Mother Mary for Her Most Holy Divine Loving Wisdom and Guidance.
Be open and honest with your Parents if pregnant, in order for your health and the Baby’s health to be taken care of straight away. Do NOT become depressed about having a Baby (any Child is God’s most Loving, unique, special GIFT He can give any Woman throughout their Life) and if you are expecting, it is God, The Holy Spirit and Jesus’ Blessing to you and your Family.
If not pregnant, it is always the best concept to become firm friends for at least 6 - 12 months before sleeping together and by that time, hopefully engaged to be Married. (Other physical relations without fully having sexual intercourse). If the guy loves you, he will wait!
I have witnessed the surprise births of so many young people (single and married) and the most wonderful Christian teachings a Baby/Child has brought into so many families and extended families. Have a chat to your boyfriend and put out some possible scenarios for your future together regardless of whether you are pregnant or not ie (a) Christian Marriage Preparation with a Priest, (b) Faith and Marriage, (c) How and where you would live as a Family, (d) ways in raising your child together and so forth. If your boyfriend takes off after the chat; he is not right for you Megan.
If this fellow is fine to engage in sexual relations in his twenties as a young man, then in my opinion, you should be communicating with him about the consequences of pregnancy risks, Faith, Religion and Marriage, giving birth, raising your child, financially supporting your child/home base/bill paying/child raising costs and the list progresses.
There are dozens of Christian organisations in each Country supporting single people with pregnancies, and if you are expecting, do not hesitate to contact them Megan.
Love and best wishes.