How can I catch up in units to transfer by the end of this year?

So you need to get 44 credit hours in what... three semesters (fall, spring, and summer)? That's doable. You have a few options: you could take 16 credit hours in the fall, another 16 in the spring, and then 12 in the summer, or you could take 18 in the fall, 18 in the spring, and 8 in the summer. There's really no feasible way to do all those in two semesters (fall and spring) because that would be 22 credit hours per semester and if you struggled last semester, you'd probably want to take it easy rather than pushing yourself to do 22. I would talk to the school you're looking to transfer to and ask if you can still apply to transfer for the Fall 2018 semester even though you'll be finishing up the last of your transfer units during Summer 2018. If they say yes, then figure out what classes will add up to 44 credits total and get to work!

To get 44 credits by the end of the year is not possible.

1. There is usually a cap of 15-16 credit units per semester. You need to check the max your school. (usually it is 5 classes)

2. You already seem to be overwhelmed with just 3 classes so adding at least 2 more will not help.

You appear to need 3 semesters with a full-time courseload of 15-16 credits per semester. You are not going to take enough classes to earn 22 or more credits per semester to do it in two. Besides, you have not been earning very good grades & dropping classes. That shows you are not an exceptionally good student, which is what it takes to handle even 15-16 credits per term with the kind of grades you need. You seem very unrealistic.