Rolled over on his own!

My 3.5 month old just started rolling into his tummy on his own! I can't believe how fast he is growing up! Last night was the first night we kept one arm our of his Love to Dream sleep sack, fortunately it up as successful and he slept as well as he normally does! But I'm terrified for the up coming weeks of him actually turning over in his bassinet and freaking out from not being able to turn back over, the 4 month sleep regression, him starting daycare on Monday, and me staring back at a very stressful job in Monday! So much going on and so many changes, just looking for some encouragement and advice for anyone in similar situations, I guess... Thanks in advance! Pictures of him rolled over. :)