MD- There are so many plank variations that honestly you could just do some of those for 40 seconds, take a 20 second break, and do another for 40 seconds. I've been doing that and I can hold a regular plank for 2 minutes now.
Some variations are spiderman plank (pull one leg in, tap it to the ground so your foot is next to your knee, put it back, repeat on the other side).
Dolphin- get into regular plank position but then do kind of a downward dog pose- lift your hips up high.
Side planks- pretty self-explanatory
Commando- this one's tough and I can barely do it for 40 seconds but you just go back and forth between full plank and elbow plank using your arms one at a time
Single arm planks, plank hip dips, and I forget the name but you put your feet to the one side then the other.

Sorry, I just love planks

wfc- I'm sorry you're not feeling well. I hope it is just PMS because I know how much you can't tolerate the haldol. Find some way to treat yourself

Mm-