Uploading Images that are bigger than 4MB

Hi! So for my vertical photos I have resized them to 1000in wide in Preview on my Macbook. Once I save it and try uploading the photos to Wordpress, it tell's me I can't even upload the photo because it's 4.5 MB and exceeds the uploading size of 4 MB. I have googled around and found that the only ways to decrease the MB are through saving as a jpeg and cropping the photo. I have saved as a JPG and it didn't decrease, and obviously cannot crop the photo's so I'm not sure what to do. 

Thanks in advance!

Victoria