Puppy play or puppy aggression?

Hi first time puppy owner over here! My fully vaxxed almost 5 month old heeler/pit mix that we’ve had since he was 8 weeks old has recently had what’s starting to become some concerning behavior. he sleeps in his crate overnight for about 7 to 8 hours. wake up around 6:30am, we go out for potty right away, always poops & pees & sometimes (ab 2x a week) if no one is at the dog park in our neighborhood we’ll go there for 5- 10 mins of play. back in for his breakfast while i make my coffee & then all hell breaks loose for the day. 🥲 this has only started maybe 2 weeks ago. Before then what i’ve read & assumed was normal land shark puppy behavior happened here & there throughout the day but had a mostly sweet boy. Now it seems like im constantly fighting him off my pants or socks which all have holes in them from his biting & pulling. so i mostly wear shorts & no socks around the house now. So now he’ll nip at my heels & calves. i’m not allowed to do nothing. lol if i’m cooking or seemingly “busy” he’s fine ? (for the most part) but recently he’s getting less patient. even then he’s barking & growling while trying to “attack me” not full on latches on skin or anything like that but lots of lunging & nipping while barking & growling. i assume it’s him playing bc his tail will be wagging? recently he’ll be sitting on the couch watching me in the kitchen & then charge at me with a growl & bark A LOT & lunge & nip at my legs. if i’m sitting on the couch he’ll jump on me & BARK & growl & nip me everywhere. & nothing will seem to calm him down except if i immediately go into training with his treats. he has lots of toys & chews. he loves his benebone. ive tried redirecting with chews, i’ve tried walking into a different room & putting MYSELF in timeout for 30 seconds & come back into the room. but the behavior just immediately continues. we do our training a couple times for 5-10 mins during the day. we play with his toys together. he has puzzle treats kongs mats. everything. so i doubt it’s that he’s bored or under stimulated ? he goes down for his naps every couple of hours. but i’m not sure if he’s actually sleeping the whole time. he doesn’t bark or whine in his crate & goes in happily. so idk. i know he’s teething & has begun to lose some teeth so i want to chalk it up to that but this morning he did kinda scare me with the behavior. on the walk back into my apartment after his walk he attacked my slippers & was growling at them in the hallway i had to pick him up & carry him back inside. then after he ate breakfast he jumped on the couch & was barking rather close to my face on the couch while nipping me all over my arms. i had to pop him in the crate bc like i said i got scared :/ this just happened then came to reddit to type this. this behavior is starting to get to me a little. i love him so much, but it’s obviously stressful & i don’t know what else to do. does this behavior sound normal ? or should i begin to worry ? any advice ? thank you in advance 🥹

edit : to add he’s a good boy out in public. we take him for dinner dates & sit outside. he mostly sits at our feet & people watches. we’ve been teaching him “focus” so when other dogs go by he focuses on us bc he was getting a little reactive to other dogs, whining & wanting to say hi & play. nothing aggressive there. loves attention from strangers. & is sweet outside the house. so this behavior seemingly only happens inside ? :/