You are probably exporting JPG’s @ 300 DPI which is leading to too high of a resolution for screen/web usage.
If you are trying to upload a screen resolution file, 1600px is probably the max width you want to use. Since Indesign has limited options when you export try starting at:
Quality: Max, Format: Baseline, PPI: 200, Color RGB - see what size that gives you. You can also try lowering the PPI to 150 which will give you a 1200px wide image (which is still fine for a page layout on a high res screen).
Those should be much smaller images. If your page layout is 200" long, thats another story - try breaking it up into multiple images.
Lastly, if your images are still that large you should export them as a PDF or TIFF, bring them into Photoshop and use Photoshops Save for Web feature to tweak the level of compression and resolution.
Remember, pixels matter on the web/screen, not “DPI”. Most students just check the 300 DPI box and think that everything is good.