Hello... I have a question about sparring...

I'm very new to kung fu. A month and a half so far. Sifu always pairs the new students up with experienced students, they have more control and are able to teach me stuff other than just pummel me into the wall.

Rules for our sparring matches are no face, no groin, and light contact. We wear sparring gloves and mouth guard thingies.

Lately I've been sparring people other than high belts, they aren't available all the time, and I don't want to spar with someone holding back all the time. A couple people in the class have a tactic in which they constantly attack. As a result they don't defend too much, but it's very hard to counter, cause I'm constantly trying to block every attack.

What can I do to defeat someone who is constantly attacking?

They seem to have unlimited stamina for throwing punches, and I am already winded from blocking so much. A few people have told me I should try to grab an arm and throw some punches in, but advice is badly needed

I'm a pretty big guy, 6' 232 lbs. I was very out of shape before kung fu but am noticing a difference after a month and a half. I need more stamina to fight longer, I know it will come, but some advice in improving that would we very welcome too...