Is my printer over extruding? I'm getting some slight pooling on the end of straight lines on my Ender-3

Is this due to over extruding? Or some other issue?
It looks like you some of your layers are printing with 100% infill.

If you are noticing plastic still coming out at the end of lines then I think your pressure in the nozzle is high when it is getting to the end of those lines and that pressure is pushing out the extra plastic. 

That could be because your over extruding, but if it is only happening on layers where you are printing with 100% infill it could also be because lines are too close together and so when your trying to push out plastic to fill all the gaps in the model the pressure is building up in the nozzle because the gaps in the infill are to small for the amount of plastic the printer is trying to push into them. 

I would see if it is happening on all your lines or is it worse on layers where the printer is printing 100% infill. Then maybe try adjusting the amount the printer is extruding and see how it changes the print. 

Adjusting the speed could also make a difference. And some slicers have a setting to tell the printer to coast at the end of a line so the printer will stop extruding just before finishing a line as well. If you think the other setting are all tuned as good as you can get them then trying the coast setting might help for the model you are trying to print.