Stuck at 2 minutes? Are you training exclusively dry? You should if you don't have a buddy. Don't go into the water for breathhold training/diving without a dedicated buddy who is watching you like a hawk.
A freediving course is always good to start with.
I did and this is what we had to do in static: (we did it in the water, but you should do it dry if you don't have a buddy!)
0) Get relaxed: lay down.
1) Do your breathe up: relaxed breathing to reduce your heart rate. Don't hyperventilate: make sure your exhales are at least twice as long as your inhales. (Three and four times longer is even better, but you have to be able to stand that pace.) Inhale fully: belly and chest expanding. Exhale: do NOT blow out the air forcefully: instead, restrict the opening of your mouth to make the air flow slower by pouting your lips and putting your tongue behind your teeth. (This results in the famous snake SSSSSS sound.)
2) after 2-3 minutes of this breathe up: last exhale: really push out as much air as you can. Then take the biggest breath you can (belly and chest expanding!) and hold it. Until the first contraction. Stop right there and breathe as much as you need.
3) repeat step 1 and 2 a few times, but with each new breathhold add 15 sec to the contraction phase. This will make you aware of how they feel. Really do try to cope with them and let them flow. Don't tense up your muscles (stomach, throat, mouth, belly). Let them come like waves. Try to relax (physically) as much as you can and then some.
If you really find it hard to add 15 seconds, add 10, or 5 instead of 15 with each new breathhold.
So: first breathhold = until first contraction
Second hold: until first contraction + 15 sec
Thirtd hold: until first contraction + 30 sec
Etc. ...
Bare in mind that this might work better in the water as the mammalian dive reflex is activated better/quicker/more(?) in the water...
(Still, when in the water, have a buddy, can't stress that enough!)
About contractions, Go Freediving happens to have written a great article about them:
http://gofreediving.co.uk/what-are-diaphragm-contractions-when-we-freedive
Have fun, keep safe and let us know how you are doing!