What should I do?

Continue with the 18/6 light schedule. If the plant is really flowering, then it won't reveg

A photoperiod can't / will nerver flower under a 18/6 schedule. You can see pistols that are showing the plant sex but that's it . So continue with a 18/6 and you will have NO flowering or else you can consider your plant as an autoflowering strain PS : reveg is not a monster cropping as you can reveg a plant that you've already harvested to keep it as a mother plant or to induce a second floxering after reveg ! Monster cropping is a method that require reveg but reveg ain't monster cropping

reveg is a technic called "monster cropping".... and u can use it for two reasons : cloning a mother plant in flow to clone new plant ( will give you monster plant later )or play with your plant with a cycle of 12/12 during 2 weeks, then reveg to 18/6 during 2 weeks again before a new cycle of 12/12 to the end of flowering. the goal is to play with the level of cytokinin phytohormones produces by the plant to increase new shoots production But in your case if i understand well u are in a 18/6 and the plant entered in flowering state.....2 possibilities : do you know the exact lineage of your seed ?? it could be a cross unstable with photos's and auto's.....if not... it could only due to a genetic disorder with another phytohormone called florigen.... a flowering-inducing hormone.... her role is to trigger the flow with the right photoperiod.... it s difficult to be affirmative cause i can't see pics or any diary....but in that case it could be a benediction for ur crop and not for your electricity bill 😚 hope this can help you....have a nice grow

Something doesn't seem/sound right with this whole situation.... Are you sure your on 18-6.. 18 hours on and 6 off?... Because your plant actually looks closer to a 12-12 from seed. It doesn't have that bushy look like it should from being in Veg for 4-5 weeks.. Your plant looks healthy kind of stretchy but very healthy.. But it definitely is lacking in the "bushy" department.