Is it hard being a mom and engineer?

Hi Emma.  Yes, I would say that there are times where I must choose between my career and my family.  However, I think this is true for any working mother and is not specific to engineers.  In my case, I have a strong support system and a supportive employer.  My employer is flexible with documented policies that enable working mothers to balance both career and family.  My family is also supportive and understanding that sometimes, work will intrude on our personal time.  It is not easy to have a household with two working parents.  You have be adaptable, set boundaries for yourself and your career, and have realistic expectations.  You can't do everything but the good news is that you don't have to.  Accept help where you can get it.  My husband is my partner in prioritizing and accomplishing tasks.  I'm proud of my career and even more proud of my family.  I'm home to get my kids on the bus in the morning and I tuck them in almost every night.  I spend most of my weekends with my husband and kids.  I give my all during the hours I'm at work and do it again for my family at home.  It is exhausting but very rewarding.  There are moments/days where I feel like I'm failing at both but those days are not often.
Regarding your lack of interest in science... it depends on what you mean by that.  I was the opposite, I loved my biology and chemistry classes.  Physics and math were OK.  Mechanical engineering is A LOT of physics.  But its not always physics by the book.  Mechanical engineering is a very diverse field that can lead you in a lot of different directions.  Some of them will be very heavy on theory and others are very practical, hands on experiences.  Either way, you have to love to learn new things and problem solving.  Being a good engineer is a way to think about things - frame a problem, being creative in the solutions, and then communicating what you've found to others.  Just because high school science isn't your favorite , you can still be an excellent engineer and love doing it.  Science has a way of sneaking into everything we do.   Its not just about enjoying a class.